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  • Question 1 - Which one of the following statements is true of glucagon? ...

    Incorrect

    • Which one of the following statements is true of glucagon?

      Your Answer: Inhibits gluconeogenesis

      Correct Answer: Produced in response to an increase of amino acids

      Explanation:

      Glucagon is a polypeptide protein that is synthesized by the alpha cells of the pancreatic islets of Langerhans. It is released in response to low blood sugar levels and the presence of amino acids. Glucagon is responsible for elevating the levels of glucose and ketones in the bloodstream.

      Glucagon: The Hormonal Antagonist to Insulin

      Glucagon is a hormone that is released from the alpha cells of the Islets of Langerhans in the pancreas. It has the opposite metabolic effects to insulin, resulting in increased plasma glucose levels. Glucagon functions by promoting glycogenolysis, gluconeogenesis, and lipolysis. It is regulated by various factors such as hypoglycemia, stresses like infections, burns, surgery, increased catecholamines, and sympathetic nervous system stimulation, as well as increased plasma amino acids. On the other hand, glucagon secretion decreases with hyperglycemia, insulin, somatostatin, and increased free fatty acids and keto acids.

      Glucagon is used to rapidly reverse the effects of hypoglycemia in diabetics. It is an essential hormone that plays a crucial role in maintaining glucose homeostasis in the body. Its antagonistic relationship with insulin helps to regulate blood glucose levels and prevent hyperglycemia. Understanding the regulation and function of glucagon is crucial in the management of diabetes and other metabolic disorders.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 2 - A 58-year-old man with chronic pancreatitis of many years develops pancreatic insufficiency. What...

    Correct

    • A 58-year-old man with chronic pancreatitis of many years develops pancreatic insufficiency. What substance will be absorbed normally?

      Your Answer: Folic acid

      Explanation:

      The digestion of fat necessitates the presence of pancreatic lipase, while the absorption of protein and B12 is aided by proteases. Folate digestion, on the other hand, does not rely on the pancreas.

      Pancreatic Secretions and their Regulation

      Pancreatic secretions are composed of enzymes and aqueous substances, with a pH of 8 and a volume of 1000-1500ml per day. The acinar cells secrete enzymes such as trypsinogen, procarboxylase, amylase, and elastase, while the ductal and centroacinar cells secrete sodium, bicarbonate, water, potassium, and chloride. The regulation of pancreatic secretions is mainly stimulated by CCK and ACh, which are released in response to digested material in the small bowel. Secretin, released by the S cells of the duodenum, also stimulates ductal cells and increases bicarbonate secretion.

      Trypsinogen is converted to active trypsin in the duodenum via enterokinase, and trypsin then activates the other inactive enzymes. The cephalic and gastric phases have less of an impact on regulating pancreatic secretions. Understanding the composition and regulation of pancreatic secretions is important in the diagnosis and treatment of pancreatic disorders.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 3 - A 60-year-old woman complains of persistent diarrhoea, wheezing, and flushing. During the physical...

    Incorrect

    • A 60-year-old woman complains of persistent diarrhoea, wheezing, and flushing. During the physical examination, an irregular pulsatile hepatomegaly and a pansystolic murmur that is most pronounced during inspiration are detected. What diagnostic test could provide insight into the probable underlying condition?

      Your Answer: Abdominal thoracic CT

      Correct Answer: Urinary 5-HIAA (5-hydroxyindole acetic acid)

      Explanation:

      Carcinoid Syndrome and its Diagnosis

      Carcinoid syndrome is characterized by the presence of vasoactive amines such as serotonin in the bloodstream, leading to various clinical features. The primary carcinoid tumor is usually found in the small intestine or appendix, but it may not cause significant symptoms as the liver detoxifies the blood of these amines. However, systemic effects occur when malignant cells spread to other organs, such as the lungs, which are not part of the portal circulation. One of the complications of carcinoid syndrome is damage to the right heart valves, which can cause tricuspid regurgitation, as evidenced by a pulsatile liver and pansystolic murmur.

      To diagnose carcinoid syndrome, the 5-HIAA test is usually performed, which measures the breakdown product of serotonin in a 24-hour urine collection. If the test is positive, imaging and histology are necessary to confirm malignancy.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 4 - A 56-year-old woman visits her primary care physician with concerns about recent weight...

    Correct

    • A 56-year-old woman visits her primary care physician with concerns about recent weight gain. She reports maintaining her usual diet and exercise routine, but has noticed her face appearing rounder and the development of purplish stretch marks on her abdomen. During the exam, her heart rate is 89 beats per minute, respiratory rate is 16 breaths per minute, and blood pressure is 157/84 mmHg. Her waist circumference measures 41 inches and her body mass index is 28 kg/m2. What is one effect of the primary hormone involved in this patient's condition?

      Your Answer: Upregulation of alpha-1-adrenoceptors on arterioles

      Explanation:

      The patient is exhibiting symptoms consistent with a state of elevated cortisol levels, known as Cushing syndrome. These symptoms include recent weight gain, a round face (moon face), abdominal striae, high blood pressure, and truncal obesity. Cushing syndrome can have various causes, including the use of glucocorticoids or an ectopic ACTH secretion.

      Elevated cortisol levels can lead to an increase in blood glucose levels, putting individuals at risk for hyperglycemia and diabetes. Cortisol can also suppress the immune system, inhibiting the production of prostaglandins, leukotrienes, and interleukin-2, and decreasing the adhesion of white blood cells. Additionally, cortisol can up-regulate alpha-1-adrenoceptors on arterioles, resulting in high blood pressure. High cortisol levels can also decrease osteoblast activity, leading to weakened bones, and reduce fibroblast activity and collagen synthesis, resulting in delayed wound healing. The abdominal striae seen in patients with high cortisol levels are typically due to decreased collagen synthesis.

      Causes of Cushing’s Syndrome

      Cushing’s syndrome is a condition that can be caused by both endogenous and exogenous factors. However, it is important to note that exogenous causes, such as the use of glucocorticoid therapy, are more common than endogenous ones. The condition can be classified into two categories: ACTH dependent and ACTH independent causes.

      ACTH dependent causes of Cushing’s syndrome include Cushing’s disease, which is caused by a pituitary tumor secreting ACTH and producing adrenal hyperplasia. Ectopic ACTH production, which is caused by small cell lung cancer, is another ACTH dependent cause. On the other hand, ACTH independent causes include iatrogenic factors such as steroid use, adrenal adenoma, adrenal carcinoma, Carney complex, and micronodular adrenal dysplasia.

      In some cases, a condition called Pseudo-Cushing’s can mimic Cushing’s syndrome. This is often caused by alcohol excess or severe depression and can cause false positive results in dexamethasone suppression tests or 24-hour urinary free cortisol tests. To differentiate between Cushing’s syndrome and Pseudo-Cushing’s, an insulin stress test may be used.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 5 - A 14-year-old boy is brought to the clinic by his mother due to...

    Incorrect

    • A 14-year-old boy is brought to the clinic by his mother due to concerns about his height compared to other boys his age. The boy also shares that he often receives comments about his appearance, with some likening him to a toy doll. What can be inferred about the pattern of hormone release that he may be lacking?

      Your Answer: Secreted throughout the day

      Correct Answer: It is released in a pulsatile manner

      Explanation:

      The doll-like appearance of the boy in his presentation suggests that he may be suffering from growth hormone deficiency, which can cause short stature, forehead prominence, and maxillary hypoplasia. The hypothalamus controls the release of growth hormone through the pulsatile release of growth hormone releasing hormone. Therefore, measuring GHRH levels is not a useful method for investigating growth hormone deficiency.

      Understanding Growth Hormone and Its Functions

      Growth hormone (GH) is a hormone produced by the somatotroph cells in the anterior pituitary gland. It plays a crucial role in postnatal growth and development, as well as in regulating protein, lipid, and carbohydrate metabolism. GH acts on a transmembrane receptor for growth factor, leading to receptor dimerization and direct or indirect effects on tissues via insulin-like growth factor 1 (IGF-1), which is primarily secreted by the liver.

      GH secretion is regulated by various factors, including growth hormone releasing hormone (GHRH), fasting, exercise, and sleep. Conversely, glucose and somatostatin can decrease GH secretion. Disorders associated with GH include acromegaly, which results from excess GH, and GH deficiency, which can lead to short stature.

      In summary, GH is a vital hormone that plays a significant role in growth and metabolism. Understanding its functions and regulation can help in the diagnosis and treatment of GH-related disorders.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 6 - Which of the following explains the mechanism by which PTH increases serum calcium...

    Incorrect

    • Which of the following explains the mechanism by which PTH increases serum calcium levels?

      Your Answer: Direct stimulation of osteoclasts to absorb bone with release of calcium.

      Correct Answer: Activation of vitamin D to increase absorption of calcium from the small intestine.

      Explanation:

      The activity of the 1-α-hydroxylase enzyme, which converts 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (the active form of vitamin D), is increased by PTH. Osteoblasts mediate the effects of PTH on osteoclasts, as osteoclasts do not have a PTH receptor.

      Understanding Parathyroid Hormone and Its Effects

      Parathyroid hormone is a hormone produced by the chief cells of the parathyroid glands. Its main function is to increase the concentration of calcium in the blood by stimulating the PTH receptors in the kidney and bone. This hormone has a short half-life of only 4 minutes.

      The effects of parathyroid hormone are mainly seen in the bone, kidney, and intestine. In the bone, PTH binds to osteoblasts, which then signal to osteoclasts to resorb bone and release calcium. In the kidney, PTH promotes the active reabsorption of calcium and magnesium from the distal convoluted tubule, while decreasing the reabsorption of phosphate. In the intestine, PTH indirectly increases calcium absorption by increasing the activation of vitamin D, which in turn increases calcium absorption.

      Overall, understanding the role of parathyroid hormone is important in maintaining proper calcium levels in the body. Any imbalances in PTH secretion can lead to various disorders such as hyperparathyroidism or hypoparathyroidism.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 7 - A 55-year-old male comes to see you with worries about his weight. He...

    Incorrect

    • A 55-year-old male comes to see you with worries about his weight. He has a BMI of 32 and you suspect he may have metabolic syndrome. What is one of the diagnostic criteria for this condition?

      Your Answer: HDL-cholesterol >50 mg/dL

      Correct Answer: Dyslipidaemia

      Explanation:

      Metabolic syndrome is a group of risk factors for cardiovascular disease that are closely related to insulin resistance and central obesity.

      The diagnostic criteria for metabolic syndrome vary widely, but the International Diabetes Federation (IDF) and American Heart Association (AHA) have established their own criteria, which are commonly used. A diagnosis is made if three or more of the following criteria are present: increased waist circumference (depending on ethnicity) or a BMI greater than 30, dyslipidemia with elevated triglycerides greater than 150 mg/dL or reduced HDL-cholesterol, hypertension, and impaired glucose tolerance.

      The Physiology of Obesity: Leptin and Ghrelin

      Leptin is a hormone produced by adipose tissue that plays a crucial role in regulating body weight. It acts on the hypothalamus, specifically on the satiety centers, to decrease appetite and induce feelings of fullness. In cases of obesity, where there is an excess of adipose tissue, leptin levels are high. Leptin also stimulates the release of melanocyte-stimulating hormone (MSH) and corticotrophin-releasing hormone (CRH), which further contribute to the regulation of appetite. On the other hand, low levels of leptin stimulate the release of neuropeptide Y (NPY), which increases appetite.

      Ghrelin, on the other hand, is a hormone that stimulates hunger. It is mainly produced by the P/D1 cells lining the fundus of the stomach and epsilon cells of the pancreas. Ghrelin levels increase before meals, signaling the body to prepare for food intake, and decrease after meals, indicating that the body has received enough nutrients.

      In summary, the balance between leptin and ghrelin plays a crucial role in regulating appetite and body weight. In cases of obesity, there is an imbalance in this system, with high levels of leptin and potentially disrupted ghrelin signaling, leading to increased appetite and weight gain.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 8 - A 28-year-old woman complains of amenorrhoea and galactorrhoea for the past six months....

    Correct

    • A 28-year-old woman complains of amenorrhoea and galactorrhoea for the past six months. She has not been taking any medication and has been in good health otherwise. A pregnancy test has come back negative. What would be the most suitable investigation for this patient?

      Your Answer: Prolactin concentration

      Explanation:

      Galactorrhoea and Prolactinomas

      Galactorrhoea is a condition where breast milk is secreted, commonly seen during pregnancy and the early postpartum period. However, if a pregnancy test is negative, it may indicate the presence of a prolactinoma. Prolactinomas are tumors that develop in the pituitary gland, which can be either small or large. These tumors cause symptoms such as menstrual disturbance, infertility, and galactorrhoea due to the secretion of prolactin. Macroprolactinomas can also cause visual field defects, headache, and hypopituitarism due to their mass effect on the pituitary gland. Women with prolactinomas tend to present early due to menstrual cycle and fertility issues, while men may present later.

      The diagnosis of prolactinomas is made by measuring serum prolactin levels and performing MRI imaging of the pituitary gland. Serum prolactin levels are typically several thousand, with a reference range of less than 690 U/L. Elevated prolactin levels can also be caused by pregnancy and lactation, hypothyroidism, and certain medications such as antipsychotics, anti-depressants, and anti-convulsants.

      The treatment for prolactinomas involves drugs such as bromocriptine or cabergoline, which work by inhibiting prolactin release through the dopamine system. These drugs can cause significant tumor shrinkage over several weeks and months of treatment. Patients are typically monitored with serum prolactin levels and MRI scans for several years while continuing the medication. Some patients may be able to stop the medication without any further issues, while others may experience a relapse and need to resume treatment.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 9 - An aged woman with malabsorption and weight loss was diagnosed with small bowel...

    Correct

    • An aged woman with malabsorption and weight loss was diagnosed with small bowel amyloidosis. She was initially found to have osteomalacia and hypocalcemia. Despite receiving total parenteral nutrition with sufficient calcium replacement for the past seven days, she remained hypocalcemic. Which electrolyte deficiency is most likely responsible for this condition?

      Your Answer: Magnesium

      Explanation:

      Magnesium deficiency may occur in patients with malabsorption, even if they receive magnesium through TPN feeds, as it may not be enough to compensate for their losses. Serum calcium levels are not affected by sodium, phosphate, and potassium.

      The Importance of Magnesium and Calcium in the Body

      Magnesium and calcium are essential minerals in the body. Magnesium plays a crucial role in the secretion and action of parathyroid hormone (PTH) on target tissues. However, a deficiency in magnesium can cause hypocalcaemia and make patients unresponsive to calcium and vitamin D supplementation.

      The body contains 1000 mmol of magnesium, with half stored in bones and the rest in muscle, soft tissues, and extracellular fluid. Unlike calcium, there is no specific hormonal control of magnesium. Hormones such as PTH and aldosterone affect the renal handling of magnesium.

      Magnesium and calcium also interact at a cellular level. A decrease in magnesium levels can affect the permeability of cellular membranes to calcium, leading to hyperexcitability. Therefore, it is essential to maintain adequate levels of both magnesium and calcium in the body for optimal health.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 10 - A 27-year-old man who has been morbidly obese for the past six years...

    Correct

    • A 27-year-old man who has been morbidly obese for the past six years is being evaluated at the surgical bariatric clinic. Which hormone release would lead to an increase in appetite in this patient?

      Your Answer: Ghrelin

      Explanation:

      Leptin is a hormone that reduces appetite, while ghrelin is a hormone that stimulates appetite. Although thyroxine can increase appetite, it is not consistent with the symptoms being described.

      The Physiology of Obesity: Leptin and Ghrelin

      Leptin is a hormone produced by adipose tissue that plays a crucial role in regulating body weight. It acts on the hypothalamus, specifically on the satiety centers, to decrease appetite and induce feelings of fullness. In cases of obesity, where there is an excess of adipose tissue, leptin levels are high. Leptin also stimulates the release of melanocyte-stimulating hormone (MSH) and corticotrophin-releasing hormone (CRH), which further contribute to the regulation of appetite. On the other hand, low levels of leptin stimulate the release of neuropeptide Y (NPY), which increases appetite.

      Ghrelin, on the other hand, is a hormone that stimulates hunger. It is mainly produced by the P/D1 cells lining the fundus of the stomach and epsilon cells of the pancreas. Ghrelin levels increase before meals, signaling the body to prepare for food intake, and decrease after meals, indicating that the body has received enough nutrients.

      In summary, the balance between leptin and ghrelin plays a crucial role in regulating appetite and body weight. In cases of obesity, there is an imbalance in this system, with high levels of leptin and potentially disrupted ghrelin signaling, leading to increased appetite and weight gain.

    • This question is part of the following fields:

      • Endocrine System
      9.8
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  • Question 11 - A 19-year-old man was recently admitted to hospital with invasive meningococcal disease. He...

    Incorrect

    • A 19-year-old man was recently admitted to hospital with invasive meningococcal disease. He has no other medical history but is now complaining of extreme fatigue, light-headedness and rapid weight loss. He has also noticed his skin appears much more tanned than usual. His BP is 98/60 mmHg. Capillary glucose is found to be 2.2 mmol/L.

      Hb 135 g/L Male: (130 - 180)
      Platelets 280 * 109/L (150 - 400)
      WBC 5.5 * 109/L (4.0 - 11.0)
      Na+ 128 mmol/L (135 - 145)
      K+ 5.8 mmol/L (3.5 - 5.0)
      Bicarbonate 19 mmol/L (22 - 29)
      Urea 8.0 mmol/L (2.0 - 7.0)
      Creatinine 125 µmol/L (55 - 120)

      What is the most likely cause of his symptoms?

      Your Answer: Hypothyroidism

      Correct Answer: Waterhouse-Friedrichsen syndrome

      Explanation:

      Understanding Waterhouse-Friderichsen Syndrome

      Waterhouse-Friderichsen syndrome is a condition that occurs when the adrenal glands fail due to a previous adrenal haemorrhage caused by a severe bacterial infection. The most common cause of this condition is Neisseria meningitidis, but it can also be caused by other bacteria such as Haemophilus influenzae, Pseudomonas aeruginosa, Escherichia coli, and Streptococcus pneumoniae.

      The symptoms of Waterhouse-Friderichsen syndrome are similar to those of hypoadrenalism, including lethargy, weakness, anorexia, nausea and vomiting, and weight loss. Other symptoms may include hyperpigmentation, especially in the palmar creases, vitiligo, and loss of pubic hair in women. In severe cases, a crisis may occur, which can lead to collapse, shock, and pyrexia.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 12 - The medical team at a pediatric unit faces difficulty in determining the sex...

    Correct

    • The medical team at a pediatric unit faces difficulty in determining the sex of a newborn baby as the external genitalia appear ambiguous. The suspected condition is linked to an excess of androgen and a deficiency of mineralocorticoid. Can you explain the underlying pathophysiology?

      Your Answer: Deficiency of 21-alphahydroxylase

      Explanation:

      The clinical scenario described in the question is indicative of congenital adrenal hyperplasia, which is caused by a deficiency of the enzyme 21-alphahydroxylase. This leads to an increase in androgen production, resulting in virilization of genitalia in XX females, making them appear as males at birth.

      On the other hand, a deficiency of 5-alpha reductase causes the opposite situation, where genetically XY males have external female genitalia.

      Type 1 diabetes mellitus may be associated with the presence of autoantibodies against glutamic acid decarboxylase.

      A defect in the AIRE gene can lead to APECED, which is characterized by hypoparathyroidism, adrenal failure, and candidiasis.

      Similarly, a defect in the FOXP3 gene can cause IPEX, which presents with immune dysregulation, polyendocrinopathy, and enteropathy.

      Congenital adrenal hyperplasia is a genetic condition that affects the adrenal glands and can result in various symptoms depending on the specific enzyme deficiency. One common form is 21-hydroxylase deficiency, which can cause virilization of female genitalia, precocious puberty in males, and a salt-losing crisis in 60-70% of patients during the first few weeks of life. Another form is 11-beta hydroxylase deficiency, which can also cause virilization and precocious puberty, as well as hypertension and hypokalemia. A third form is 17-hydroxylase deficiency, which typically does not cause virilization in females but can result in intersex characteristics in boys and hypertension.

      Overall, congenital adrenal hyperplasia can have significant impacts on a person’s physical development and health, and early diagnosis and treatment are important for managing symptoms and preventing complications.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 13 - A 25-year-old woman has a total thyroidectomy to treat papillary carcinoma of the...

    Correct

    • A 25-year-old woman has a total thyroidectomy to treat papillary carcinoma of the thyroid. During examination of histological sections of the thyroid gland, the pathologist discovers the presence of psammoma bodies. What is the primary composition of these bodies?

      Your Answer: Clusters of calcification

      Explanation:

      Clusters of microcalcification, known as psammoma bodies, are frequently observed in papillary carcinomas.

      Thyroid cancer rarely causes hyperthyroidism or hypothyroidism as it does not usually secrete thyroid hormones. The most common type of thyroid cancer is papillary carcinoma, which is often found in young females and has an excellent prognosis. Follicular carcinoma is less common, while medullary carcinoma is a cancer of the parafollicular cells that secrete calcitonin and is associated with multiple endocrine neoplasia type 2. Anaplastic carcinoma is rare and not responsive to treatment, causing pressure symptoms. Lymphoma is also rare and associated with Hashimoto’s thyroiditis.

      Management of papillary and follicular cancer involves a total thyroidectomy followed by radioiodine to kill residual cells. Yearly thyroglobulin levels are monitored to detect early recurrent disease. Papillary carcinoma usually contains a mixture of papillary and colloidal filled follicles, while follicular adenoma presents as a solitary thyroid nodule and malignancy can only be excluded on formal histological assessment. Follicular carcinoma may appear macroscopically encapsulated, but microscopically capsular invasion is seen. Medullary carcinoma is associated with raised serum calcitonin levels and familial genetic disease in up to 20% of cases. Anaplastic carcinoma is most common in elderly females and is treated by resection where possible, with palliation achieved through isthmusectomy and radiotherapy. Chemotherapy is ineffective.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 14 - Which of the following most accurately explains how glucocorticoids work? ...

    Incorrect

    • Which of the following most accurately explains how glucocorticoids work?

      Your Answer: Activation of transmembrane tyrosine kinase systems to affect intranuclear gene transcription

      Correct Answer: Binding of intracellular receptors that migrate to the nucleus to then affect gene transcription

      Explanation:

      The effects of glucocorticoids are mediated by intracellular receptors that bind to them and are subsequently transported to the nucleus, where they modulate gene transcription.

      Corticosteroids are commonly prescribed medications that can be taken orally or intravenously, or applied topically. They mimic the effects of natural steroids in the body and can be used to replace or supplement them. However, the use of corticosteroids is limited by their numerous side effects, which are more common with prolonged and systemic use. These side effects can affect various systems in the body, including the endocrine, musculoskeletal, gastrointestinal, ophthalmic, and psychiatric systems. Some of the most common side effects include impaired glucose regulation, weight gain, osteoporosis, and increased susceptibility to infections. Patients on long-term corticosteroids should have their doses adjusted during intercurrent illness, and the medication should not be abruptly withdrawn to avoid an Addisonian crisis. Gradual withdrawal is recommended for patients who have received high doses or prolonged treatment.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 15 - A young male with a history of diabetes mellitus type 1 is admitted...

    Incorrect

    • A young male with a history of diabetes mellitus type 1 is admitted to the emergency department. He was previously found to be confused by his roommates in his room. As well as this, he complains of nausea and abdominal pain.

      An ECG is performed and shows tall tented T waves.

      A simple blood test reveals marked hyperglycemia. A urinalysis shows the presence of ketones ++.

      His bloods show the following:

      Hb 136 g/L Male: (135-180)
      Platelets 210 * 109/L (150 - 400)
      WBC 9.5 * 109/L (4.0 - 11.0)

      Na+ 137 mmol/L (135 - 145)
      K+ 7.1 mmol/L (3.5 - 5.0)
      Bicarbonate 31 mmol/L (22 - 29)
      Urea 8.0 mmol/L (2.0 - 7.0)
      Creatinine 155 µmol/L (55 - 120)

      He is given insulin, calcium gluconate and IV saline.

      What is the main mechanism as to why the patient's potassium level will decrease?

      Your Answer: IV fluids increase the clearance of potassium through kidneys

      Correct Answer: Insulin increases sodium potassium pump

      Explanation:

      Insulin stimulates the Na+/K+ ATPase pump, leading to a decrease in serum potassium levels. This is primarily achieved through increased activity of the sodium-potassium pump, which is triggered by phosphorylation of the transmembrane subunits in response to insulin. While calcium gluconate is used to protect the heart during hyperkalaemia-induced arrhythmias, it does not affect potassium levels. Although IV fluids can improve renal function and potassium clearance, they are not the primary method for reducing potassium levels. Calcium-activated potassium channels are present throughout the body and are activated by an increase in intracellular calcium levels during action potentials.

      Insulin is a hormone produced by the pancreas that plays a crucial role in regulating the metabolism of carbohydrates and fats in the body. It works by causing cells in the liver, muscles, and fat tissue to absorb glucose from the bloodstream, which is then stored as glycogen in the liver and muscles or as triglycerides in fat cells. The human insulin protein is made up of 51 amino acids and is a dimer of an A-chain and a B-chain linked together by disulfide bonds. Pro-insulin is first formed in the rough endoplasmic reticulum of pancreatic beta cells and then cleaved to form insulin and C-peptide. Insulin is stored in secretory granules and released in response to high levels of glucose in the blood. In addition to its role in glucose metabolism, insulin also inhibits lipolysis, reduces muscle protein loss, and increases cellular uptake of potassium through stimulation of the Na+/K+ ATPase pump.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 16 - You have been requested to evaluate a patient in your general practice, who...

    Incorrect

    • You have been requested to evaluate a patient in your general practice, who has come in after discovering a new lump in her neck. The patient is in her mid-40s, has no significant medical history, and does not take any regular medications.

      Upon examination, you observe a small mass in the front of the neck that moves upwards when the patient swallows. There is no associated lymphadenopathy. You refer the patient for an ultrasound and biopsy, which reveals the presence of 'Orphan Annie eyes with psammoma bodies.'

      Based on this finding, what is the most probable diagnosis?

      Your Answer: Graves' disease

      Correct Answer: Papillary thyroid cancer

      Explanation:

      The patient has a painless lump in the thyroid gland that moves on swallowing, indicating thyroid pathology. The biopsy result of Orphan Annie eyes with psammoma bodies is a characteristic finding in papillary thyroid cancer, which is a slow-growing malignancy with less likelihood of lymphadenopathy. Graves’ disease is an incorrect diagnosis as it would not present with this appearance on biopsy and would likely exhibit signs of thyrotoxicosis. A multinodular goitre also does not have this appearance and may cause a thyrotoxic state. Anaplastic carcinoma is a more aggressive thyroid malignancy that readily invades nearby tissues and has a different histological appearance with spindle cells and giant cells.

      Thyroid cancer rarely causes hyperthyroidism or hypothyroidism as it does not usually secrete thyroid hormones. The most common type of thyroid cancer is papillary carcinoma, which is often found in young females and has an excellent prognosis. Follicular carcinoma is less common, while medullary carcinoma is a cancer of the parafollicular cells that secrete calcitonin and is associated with multiple endocrine neoplasia type 2. Anaplastic carcinoma is rare and not responsive to treatment, causing pressure symptoms. Lymphoma is also rare and associated with Hashimoto’s thyroiditis.

      Management of papillary and follicular cancer involves a total thyroidectomy followed by radioiodine to kill residual cells. Yearly thyroglobulin levels are monitored to detect early recurrent disease. Papillary carcinoma usually contains a mixture of papillary and colloidal filled follicles, while follicular adenoma presents as a solitary thyroid nodule and malignancy can only be excluded on formal histological assessment. Follicular carcinoma may appear macroscopically encapsulated, but microscopically capsular invasion is seen. Medullary carcinoma is associated with raised serum calcitonin levels and familial genetic disease in up to 20% of cases. Anaplastic carcinoma is most common in elderly females and is treated by resection where possible, with palliation achieved through isthmusectomy and radiotherapy. Chemotherapy is ineffective.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 17 - A 57-year-old woman presents to the physician with a recurring blistering rash on...

    Incorrect

    • A 57-year-old woman presents to the physician with a recurring blistering rash on her hands. The rash has also affected her legs, inguinal creases, and the corners of her mouth at different times. She was diagnosed with type 2 diabetes mellitus three months ago and has occasional loose stools. The patient denies experiencing palpitations, abdominal pain, or vomiting, but reports having occasional watery stools.

      During the physical examination, the physician observes coalescing erythematous plaques with crusting and scaling at the borders and central areas of brownish induration over the lower abdomen and in the perioral skin.

      What is the most likely diagnosis for this patient?

      Your Answer: Gastrinoma

      Correct Answer: Glucagonoma

      Explanation:

      The patient is likely suffering from a glucagonoma, a rare tumor that originates from the alpha cells of the pancreas. This condition causes the excessive secretion of glucagon, resulting in hyperglycemia or diabetes mellitus. One of the characteristic symptoms of glucagonoma is necrolytic migratory erythema, a painful and itchy rash that appears on the face, groin, and limbs.

      Gastrinoma, on the other hand, does not cause a blistering rash or diabetes mellitus. However, it is often associated with abdominal pain, diarrhea, and ulceration.

      Somatostatinoma typically presents with abdominal pain, constipation, hyperglycemia, and steatorrhea, which are not present in this patient.

      VIPoma is unlikely as it usually causes intractable diarrhea, hypokalemia, and achlorhydria.

      Although zinc deficiency can cause skin lesions that resemble necrolytic migratory erythema, the patient’s recent diabetes mellitus diagnosis and lack of other symptoms make glucagonoma the more likely diagnosis.

      Glucagonoma: A Rare Pancreatic Tumor

      Glucagonoma is a rare type of pancreatic tumor that usually originates from the alpha cells of the pancreas. These tumors are typically small and malignant, and they can cause a range of symptoms, including diabetes mellitus, venous thrombo-embolism, and a distinctive red, blistering rash known as necrolytic migratory erythema. To diagnose glucagonoma, doctors typically look for a serum level of glucagon that is higher than 1000pg/ml, and they may also use CT scanning to visualize the tumor. Treatment options for glucagonoma include surgical resection and octreotide, a medication that can help to control the symptoms of the disease. Overall, glucagonoma is a rare but serious condition that requires prompt diagnosis and treatment to manage its symptoms and prevent complications.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 18 - A 23-year-old male comes to his doctor with a 5-month history of headaches,...

    Correct

    • A 23-year-old male comes to his doctor with a 5-month history of headaches, palpitations, and excessive sweating. He also mentions unintentional weight loss. Upon examination, the patient is found to be tachycardic and sweating profusely. The doctor suspects that the man may have a tumor affecting the tissue responsible for producing adrenaline.

      What is the probable location of the tumor?

      Your Answer: Adrenal medulla

      Explanation:

      The secretion of adrenaline is primarily carried out by the adrenal medulla. A patient with a phaeochromocytoma, a type of cancer that affects the adrenal medulla, may experience symptoms such as tachycardia, headaches, and sweating due to excess adrenaline production.

      The adrenal cortex, which surrounds the adrenal medulla, is not involved in adrenaline synthesis. It is responsible for producing mineralocorticoids, glucocorticoids, and androgens.

      The medulla oblongata, located in the brainstem, regulates essential bodily functions but is not responsible for adrenaline secretion.

      The parathyroid gland, which produces parathyroid hormone to regulate calcium metabolism, is not related to adrenaline secretion.

      The Function of Adrenal Medulla

      The adrenal medulla is responsible for producing almost all of the adrenaline in the body, along with small amounts of noradrenaline. Essentially, it is a specialized and enlarged sympathetic ganglion. This gland plays a crucial role in the body’s response to stress and danger, as adrenaline is a hormone that prepares the body for the fight or flight response. When the body perceives a threat, the adrenal medulla releases adrenaline into the bloodstream, which increases heart rate, blood pressure, and respiration, while also dilating the pupils and increasing blood flow to the muscles. This response helps the body to react quickly and effectively to danger. Overall, the adrenal medulla is an important component of the body’s stress response system.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 19 - A 33-year-old man arrives at the emergency department with symptoms of increased thirst...

    Correct

    • A 33-year-old man arrives at the emergency department with symptoms of increased thirst and frequent urination. He had suffered a head injury a few days ago and had previously been discharged after investigations. Upon examination, he appears dehydrated and is admitted to a medical ward. The urine osmolality test results show a low level of 250 mosmol/kg after water deprivation and a high level of 655 mosmol/kg after desmopressin administration. Based on this information, where is the deficient substance typically active?

      Your Answer: Collecting duct

      Explanation:

      The site of action for antidiuretic hormone (ADH) is the collecting ducts in the kidneys. A diagnosis of cranial diabetes insipidus, which can occur after head trauma, is confirmed by low urine osmolalities. In this condition, there is a deficiency of ADH, which is synthesized in the hypothalamus but acts on the collecting ducts to promote water reabsorption. Therefore, the hypothalamus is not the site of action for ADH, despite being where it is synthesized. The Loop of Henle and proximal convoluted tubule are also not the primary sites of action for ADH. ADH is released from the posterior pituitary gland, but its action occurs in the collecting ducts.

      Understanding Antidiuretic Hormone (ADH)

      Antidiuretic hormone (ADH) is a hormone that is produced in the supraoptic nuclei of the hypothalamus and released by the posterior pituitary gland. Its primary function is to conserve body water by promoting water reabsorption in the collecting ducts of the kidneys through the insertion of aquaporin-2 channels.

      ADH secretion is regulated by various factors. An increase in extracellular fluid osmolality, a decrease in volume or pressure, and the presence of angiotensin II can all increase ADH secretion. Conversely, a decrease in extracellular fluid osmolality, an increase in volume, a decrease in temperature, or the absence of ADH can decrease its secretion.

      Diabetes insipidus (DI) is a condition that occurs when there is either a deficiency of ADH (cranial DI) or an insensitivity to ADH (nephrogenic DI). Cranial DI can be treated with desmopressin, which is an analog of ADH.

      Overall, understanding the role of ADH in regulating water balance in the body is crucial for maintaining proper hydration and preventing conditions like DI.

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      • Endocrine System
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  • Question 20 - A 59-year-old man with a known history of type-2 diabetes comes for a...

    Correct

    • A 59-year-old man with a known history of type-2 diabetes comes for a check-up. He is currently on metformin only for his diabetes and reports compliance with the prescribed regimen.

      His HbA1c is 63 mmol/mol (target = 53mmol/mol) and the patient and clinician agree to initiate a sulfonylurea along with his metformin.

      What is the primary mode of action of the new treatment?

      Your Answer: Increases stimulation of insulin secretion by pancreatic B-cells and decreases hepatic clearance of insulin

      Explanation:

      Sulfonylureas are a type of oral hypoglycemic agent that stimulate insulin secretion by pancreatic B-cells and reduce the clearance of insulin by the liver. They are known as insulin secretagogues.

      Sulfonylureas are a type of medication used to treat type 2 diabetes mellitus. They work by increasing the amount of insulin produced by the pancreas, but only if the beta cells in the pancreas are functioning properly. Sulfonylureas bind to a specific channel on the cell membrane of pancreatic beta cells, known as the ATP-dependent K+ channel (KATP).

      While sulfonylureas can be effective in managing diabetes, they can also cause some adverse effects. The most common side effect is hypoglycemia, which is more likely to occur with long-acting preparations like chlorpropamide. Another common side effect is weight gain. However, there are also rarer side effects that can occur, such as hyponatremia (low sodium levels) due to inappropriate ADH secretion, bone marrow suppression, hepatotoxicity (liver damage), and peripheral neuropathy.

      It is important to note that sulfonylureas should not be used during pregnancy or while breastfeeding.

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      • Endocrine System
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  • Question 21 - A 55-year-old man presents to your clinic with numbness and paraesthesia in his...

    Correct

    • A 55-year-old man presents to your clinic with numbness and paraesthesia in his right thumb and index finger. His hands seem enlarged and you observe significant gaps between his teeth. Which hormone is expected to be elevated?

      Your Answer: Growth hormone

      Explanation:

      Excessive growth hormone can cause prognathism, spade-like hands, and tall stature. Patients may experience discomfort due to ill-fitting hats or shoes, as well as joint pain, headaches, and visual issues. It is important to note that gigantism occurs when there is an excess of growth hormone secretion before growth plate fusion, while acromegaly occurs when there is an excess of secretion after growth plate fusion.

      Understanding Growth Hormone and Its Functions

      Growth hormone (GH) is a hormone produced by the somatotroph cells in the anterior pituitary gland. It plays a crucial role in postnatal growth and development, as well as in regulating protein, lipid, and carbohydrate metabolism. GH acts on a transmembrane receptor for growth factor, leading to receptor dimerization and direct or indirect effects on tissues via insulin-like growth factor 1 (IGF-1), which is primarily secreted by the liver.

      GH secretion is regulated by various factors, including growth hormone releasing hormone (GHRH), fasting, exercise, and sleep. Conversely, glucose and somatostatin can decrease GH secretion. Disorders associated with GH include acromegaly, which results from excess GH, and GH deficiency, which can lead to short stature.

      In summary, GH is a vital hormone that plays a significant role in growth and metabolism. Understanding its functions and regulation can help in the diagnosis and treatment of GH-related disorders.

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      • Endocrine System
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  • Question 22 - A 50-year-old man with type 2 diabetes mellitus, who is currently on metformin,...

    Correct

    • A 50-year-old man with type 2 diabetes mellitus, who is currently on metformin, visits for his diabetic check-up. His blood sugar levels are not well-controlled and the doctor decides to prescribe gliclazide in addition to his current medication. During the consultation, the doctor discusses the potential side effects of sulfonylureas. What is a possible side effect of sulfonylureas?

      Your Answer: Hypoglycaemia

      Explanation:

      Hypoglycaemia is a significant adverse effect of sulfonylureas, including gliclazide, which stimulate insulin secretion from the pancreas. Patients taking sulfonylureas should be educated about the possibility of hypoglycaemia and instructed on how to manage it if it occurs. Acarbose commonly causes flatulence, while PPAR agonists (glitazones) can lead to fluid retention, and metformin may cause nausea and diarrhoea.

      Sulfonylureas are a type of medication used to treat type 2 diabetes mellitus. They work by increasing the amount of insulin produced by the pancreas, but only if the beta cells in the pancreas are functioning properly. Sulfonylureas bind to a specific channel on the cell membrane of pancreatic beta cells, known as the ATP-dependent K+ channel (KATP).

      While sulfonylureas can be effective in managing diabetes, they can also cause some adverse effects. The most common side effect is hypoglycemia, which is more likely to occur with long-acting preparations like chlorpropamide. Another common side effect is weight gain. However, there are also rarer side effects that can occur, such as hyponatremia (low sodium levels) due to inappropriate ADH secretion, bone marrow suppression, hepatotoxicity (liver damage), and peripheral neuropathy.

      It is important to note that sulfonylureas should not be used during pregnancy or while breastfeeding.

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      • Endocrine System
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  • Question 23 - A 30-year-old male visits his GP complaining of chronic thirst, polyuria, and nocturia...

    Incorrect

    • A 30-year-old male visits his GP complaining of chronic thirst, polyuria, and nocturia that have persisted for 4 months. He has a medical history of OCD, which was diagnosed 2 years ago. After a series of tests, the patient is diagnosed with primary polydipsia.

      What would be the probable outcome of this patient's water deprivation test?

      Your Answer: Low urine osmolality after fluid deprivation, but high after desmopressin

      Correct Answer: High urine osmolality after both fluid deprivation and desmopressin

      Explanation:

      The water deprivation test is a diagnostic tool used to assess patients with polydipsia, or excessive thirst. During the test, the patient is instructed to refrain from drinking water, and their bladder is emptied. Hourly measurements of urine and plasma osmolalities are taken to monitor changes in the body’s fluid balance. The results of the test can help identify the underlying cause of the patient’s polydipsia. Normal results show a high urine osmolality after the administration of DDAVP, while psychogenic polydipsia is characterized by a low urine osmolality. Cranial DI and nephrogenic DI are both associated with high plasma osmolalities and low urine osmolalities.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 24 - A 50-year-old woman has just had a thyroidectomy to treat medullary thyroid cancer....

    Incorrect

    • A 50-year-old woman has just had a thyroidectomy to treat medullary thyroid cancer. What is the clinical tumor marker used to screen for recurrence?

      Your Answer: Free T4

      Correct Answer: Calcitonin

      Explanation:

      Calcitonin is used in clinical practice to detect recurrence of medullary thyroid cancer. Thyroid function tests are not used for diagnosis or follow-up of malignancies. However, regular monitoring of TSH levels may be necessary for patients taking thyroxine.

      Thyroid cancer rarely causes hyperthyroidism or hypothyroidism as it does not usually secrete thyroid hormones. The most common type of thyroid cancer is papillary carcinoma, which is often found in young females and has an excellent prognosis. Follicular carcinoma is less common, while medullary carcinoma is a cancer of the parafollicular cells that secrete calcitonin and is associated with multiple endocrine neoplasia type 2. Anaplastic carcinoma is rare and not responsive to treatment, causing pressure symptoms. Lymphoma is also rare and associated with Hashimoto’s thyroiditis.

      Management of papillary and follicular cancer involves a total thyroidectomy followed by radioiodine to kill residual cells. Yearly thyroglobulin levels are monitored to detect early recurrent disease. Papillary carcinoma usually contains a mixture of papillary and colloid filled follicles, while follicular adenoma presents as a solitary thyroid nodule and malignancy can only be excluded on formal histological assessment. Follicular carcinoma may appear macroscopically encapsulated, but microscopically capsular invasion is seen. Medullary carcinoma is associated with raised serum calcitonin levels and familial genetic disease in up to 20% of cases. Anaplastic carcinoma is most common in elderly females and is treated by resection where possible, with palliation achieved through isthmusectomy and radiotherapy. Chemotherapy is ineffective.

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      • Endocrine System
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  • Question 25 - As a third year medical student working in a GP surgery, you come...

    Incorrect

    • As a third year medical student working in a GP surgery, you come across a worried 54-year-old male patient who is experiencing chest discomfort. He has recently begun taking a new tablet for his high blood pressure and suspects it may be the cause of his symptoms. During your examination, you notice bilateral non-tender glandular swellings around the areolae. There are no signs of lymphadenopathy in the axillary region, and testicular examination is normal. Which medication is most likely responsible for this clinical presentation?

      Your Answer: Bendroflumethiazide

      Correct Answer: Spironolactone

      Explanation:

      Spironolactone-Induced Gynaecomastia

      Spironolactone is a type of diuretic that helps to increase urine production by blocking aldosterone receptors in the kidneys. However, it also has anti-androgenic properties that can lead to the development of gynaecomastia, a condition where men develop breast tissue. This is because spironolactone inhibits the production of testosterone and increases the level of free oestrogen in the blood, causing the proliferation of glandular tissue in the mammary glands.

      While gynaecomastia is not commonly associated with other medications, they all have their own side effects. Aspirin, for example, can cause gastrointestinal ulceration by inhibiting COX enzymes and prostaglandin synthesis. Thiazide diuretics work by blocking the sodium chloride co-transporter in the distal convoluted tubule, which can lead to a decrease in blood volume. Loop diuretics, on the other hand, can cause severe hyponatraemia but do not affect testosterone production. Statins, which are used to lower cholesterol levels, can cause rhabdomyolysis, a serious condition where muscle tissue breaks down and releases harmful substances into the bloodstream.

      In summary, while spironolactone can be an effective diuretic, it is important to be aware of its potential side effects, including gynaecomastia. Patients should always consult with their healthcare provider before starting any new medication and report any unusual symptoms or side effects.

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      • Endocrine System
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  • Question 26 - A 9-year-old girl is being treated by a paediatrician for bedwetting at night....

    Incorrect

    • A 9-year-old girl is being treated by a paediatrician for bedwetting at night. Non-invasive methods have not yielded any results and her family is interested in trying medication. The paediatrician has approved a trial of desmopressin.

      What is the site of action of this drug?

      Your Answer: The distal tubule of the kidney

      Correct Answer: The collecting ducts of the kidney

      Explanation:

      Desmopressin is a synthetic version of antidiuretic hormone (ADH) that acts on the collecting ducts in the kidneys. ADH is released by the posterior pituitary gland in response to increased blood osmolality. By increasing the reabsorption of solute-free water in the collecting ducts, ADH reduces blood osmolality and produces small volumes of concentrated urine. This mechanism is effective in reducing the volume of urine produced overnight in cases of nocturnal enuresis (bed-wetting). The distal tubule, glomerulus, and proximal tubule are not sites of ADH action. Although the posterior pituitary gland produces ADH, it exerts its effects on the kidneys.

      Understanding Antidiuretic Hormone (ADH)

      Antidiuretic hormone (ADH) is a hormone that is produced in the supraoptic nuclei of the hypothalamus and released by the posterior pituitary gland. Its primary function is to conserve body water by promoting water reabsorption in the collecting ducts of the kidneys through the insertion of aquaporin-2 channels.

      ADH secretion is regulated by various factors. An increase in extracellular fluid osmolality, a decrease in volume or pressure, and the presence of angiotensin II can all increase ADH secretion. Conversely, a decrease in extracellular fluid osmolality, an increase in volume, a decrease in temperature, or the absence of ADH can decrease its secretion.

      Diabetes insipidus (DI) is a condition that occurs when there is either a deficiency of ADH (cranial DI) or an insensitivity to ADH (nephrogenic DI). Cranial DI can be treated with desmopressin, which is an analog of ADH.

      Overall, understanding the role of ADH in regulating water balance in the body is crucial for maintaining proper hydration and preventing conditions like DI.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 27 - Which of the following will increase the volume of pancreatic exocrine secretions? ...

    Incorrect

    • Which of the following will increase the volume of pancreatic exocrine secretions?

      Your Answer: Adrenaline

      Correct Answer: Cholecystokinin

      Explanation:

      The volume of pancreatic secretions is often increased by cholecystokinin.

      Pancreatic Secretions and their Regulation

      Pancreatic secretions are composed of enzymes and aqueous substances, with a pH of 8 and a volume of 1000-1500ml per day. The acinar cells secrete enzymes such as trypsinogen, procarboxylase, amylase, and elastase, while the ductal and centroacinar cells secrete sodium, bicarbonate, water, potassium, and chloride. The regulation of pancreatic secretions is mainly stimulated by CCK and ACh, which are released in response to digested material in the small bowel. Secretin, released by the S cells of the duodenum, also stimulates ductal cells and increases bicarbonate secretion.

      Trypsinogen is converted to active trypsin in the duodenum via enterokinase, and trypsin then activates the other inactive enzymes. The cephalic and gastric phases have less of an impact on regulating pancreatic secretions. Understanding the composition and regulation of pancreatic secretions is important in the diagnosis and treatment of pancreatic disorders.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 28 - A 12-year-old girl, previously healthy, presents to the emergency department with symptoms of...

    Correct

    • A 12-year-old girl, previously healthy, presents to the emergency department with symptoms of nausea, vomiting, and confusion. The patient's father reports his child appearing fatigued, and having increased thirst and urinary frequency over the past few days. Upon laboratory analysis, the patient's serum glucose is found to be 25 mmol/L and urinalysis is positive for ketones. The medical team initiates fluid resuscitation and insulin therapy.

      What electrolyte changes are anticipated following the treatment of this patient?

      Your Answer: Decrease in potassium levels

      Explanation:

      The Na+/K+ ATPase pump is stimulated by insulin, leading to a decrease in serum potassium levels. This effect is particularly relevant in patients with diabetic ketoacidosis, who experience insulin deficiency and hyperkalemia. It is important to monitor serum potassium levels closely during the management of diabetic ketoacidosis to avoid the potential complications of hypokalemia. Insulin does not cause a decrease in sodium levels, and its effects on calcium and phosphate homeostasis are minimal. The resolution of ketoacidosis with insulin and fluids will result in an increase in serum bicarbonate levels back to normal range.

      Insulin is a hormone produced by the pancreas that plays a crucial role in regulating the metabolism of carbohydrates and fats in the body. It works by causing cells in the liver, muscles, and fat tissue to absorb glucose from the bloodstream, which is then stored as glycogen in the liver and muscles or as triglycerides in fat cells. The human insulin protein is made up of 51 amino acids and is a dimer of an A-chain and a B-chain linked together by disulfide bonds. Pro-insulin is first formed in the rough endoplasmic reticulum of pancreatic beta cells and then cleaved to form insulin and C-peptide. Insulin is stored in secretory granules and released in response to high levels of glucose in the blood. In addition to its role in glucose metabolism, insulin also inhibits lipolysis, reduces muscle protein loss, and increases cellular uptake of potassium through stimulation of the Na+/K+ ATPase pump.

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      • Endocrine System
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  • Question 29 - A 55-year-old man comes in for his regular check-up with his GP. He...

    Correct

    • A 55-year-old man comes in for his regular check-up with his GP. He has a medical history of chronic pancreatitis and diabetes mellitus and is currently taking the maximum doses of metformin and gliclazide. During a random plasma glucose test, his levels show 18.0 mmol/l and his urinalysis reveals glycosuria with minimal ketones. The GP suspects that his body is not producing enough insulin and decides to initiate insulin therapy. Can you identify the location in the body where insulin is produced?

      Your Answer: Pancreatic beta cells

      Explanation:

      Diabetes mellitus in this patient is most likely caused by chronic pancreatitis, which has resulted in the destruction of the pancreatic endocrine cells responsible for producing endogenous insulin. These cells are located in the Islets of Langerhans and are known as pancreatic beta cells (β-cells). Other cells in the pancreas, such as alpha cells (which secrete glucagon) and delta cells (which secrete somatostatin), do not produce insulin. Similarly, gastric G cells secrete gastrin and are not involved in insulin production.

      Insulin is a hormone produced by the pancreas that plays a crucial role in regulating the metabolism of carbohydrates and fats in the body. It works by causing cells in the liver, muscles, and fat tissue to absorb glucose from the bloodstream, which is then stored as glycogen in the liver and muscles or as triglycerides in fat cells. The human insulin protein is made up of 51 amino acids and is a dimer of an A-chain and a B-chain linked together by disulfide bonds. Pro-insulin is first formed in the rough endoplasmic reticulum of pancreatic beta cells and then cleaved to form insulin and C-peptide. Insulin is stored in secretory granules and released in response to high levels of glucose in the blood. In addition to its role in glucose metabolism, insulin also inhibits lipolysis, reduces muscle protein loss, and increases cellular uptake of potassium through stimulation of the Na+/K+ ATPase pump.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 30 - A 14-year-old girl is referred to the endocrine clinic by her GP due...

    Incorrect

    • A 14-year-old girl is referred to the endocrine clinic by her GP due to bed wetting episodes. She experiences constant thirst and frequent urination. A dipstick test reveals diluted urine with low osmolality, and her blood tests show hypernatremia with high serum osmolality. Her family has a history of diabetes insipidus. What is the most suitable follow-up examination?

      Your Answer: Urinary sodium

      Correct Answer: Water deprivation test

      Explanation:

      A water deprivation test is the most appropriate method for diagnosing diabetes insipidus. This test involves withholding water from the patient for a period of time to stimulate the release of antidiuretic hormone (ADH) and monitor changes in serum and urine osmolality. Other methods such as urinary sodium or bladder ultrasound scan are not as effective in diagnosing this condition.

      The water deprivation test is a diagnostic tool used to assess patients with polydipsia, or excessive thirst. During the test, the patient is instructed to refrain from drinking water, and their bladder is emptied. Hourly measurements of urine and plasma osmolalities are taken to monitor changes in the body’s fluid balance. The results of the test can help identify the underlying cause of the patient’s polydipsia. Normal results show a high urine osmolality after the administration of DDAVP, while psychogenic polydipsia is characterized by a low urine osmolality. Cranial DI and nephrogenic DI are both associated with high plasma osmolalities and low urine osmolalities.

    • This question is part of the following fields:

      • Endocrine System
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