The combination of Insulinoma and Parathyroid diseases is suggestive of MEN 1 syndrome.
Multiple endocrine neoplasia type 1 (MEN1) is a rare hereditary tumour syndrome inherited in an autosomal dominant manner and characterized by a predisposition to a multitude of endocrine neoplasms primarily of parathyroid, entero-pancreatic, and anterior pituitary origin, as well as non-endocrine neoplasms.
Other endocrine tumours in MEN1 include foregut carcinoid tumours, adrenocortical tumours, and rarely pheochromocytoma. Nonendocrine manifestations include meningiomas and ependymomas, lipomas, angiofibromas, collagenomas, and leiomyomas.

Primary hyperparathyroidism (PHPT), due to parathyroid hyperplasia is the most frequent and usually the earliest expression of MEN-1, with a typical age of onset at 20–25 years.

Acromegaly occurs due to excessive action of insulin-like growth factor I (IGF-I) after the growth plate cartilage fuses in adulthood.
It can be an insidious disease. Symptoms, which may precede diagnosis by several years, can be divided into the following groups:
1. Symptoms due to local mass effects of an intracranial tumour
Tumour damage to the pituitary stalk may cause hyperprolactinemia (Increased blood prolactin levels associated with galactorrhoea) due to loss of inhibitory regulation of prolactin secretion by the hypothalamus
2. Symptoms due to excess of GH/IGF-I including:
– Hyperhidrosis (Not hypohidrosis)
– Arthritis
– Peripheral Neuropathies e.g. Carpal Tunnel Syndrome

The patient is most likely to have Bulimia nervosa. A young girl with a low body mass contributes to the low urea. Hypokalaemia and hyponatraemia are due to vomiting. Her urine sodium is also low.
– In Addison’s diseases, there are low levels of sodium and high levels of potassium in the blood. In acute adrenal crisis: The most consistent finding is elevated blood urea nitrogen (BUN) and creatinine. Urinary and sweat sodium also may be elevated.
– In Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) there is hyponatremia with corresponding hypo-osmolality, continued renal excretion of sodium, urine less than maximally dilute and absence of clinical evidence of volume depletion.

It has been determined that HPV infection is the most powerful epidemic factor. This virus is needed, but not sufficient for the development of cervical cancer.
The WHO’s International Agency for Research on Cancer (IARC) classified HPV infection as carcinogenic to humans (HPV types 16 and 18), probably carcinogenic (HPV types 31 and 33) and possibly carcinogenic (other HPV types except 6 and 11).
Tobacco smoking, the use of contraceptives, and the number of births are factors that showed no statistically significant deviations in the studied population compared to other countries in the region, as well as European countries. They have an equal statistical significance in all age groups.

Klinefelter syndrome (KS), the most common human sex chromosome disorder 47,XXY. It is characterized by hypogonadism (micro-orchidism, oligospermia/azoospermia) and gynecomastia in late puberty. If Klinefelter syndrome is not diagnosed prenatally, a patient with 47,XXY karyotype may demonstrate various subtle, age-related clinical signs that would prompt diagnostic testing. These include the following:
Infants: Hypospadias, small phallus, cryptorchidism.
Toddlers: Developmental delay (especially expressive language skills), hypotonia.
Older boys and adolescent males: Tall stature; delayed or incomplete pubertal development with eunuchoid body habitus; gynecomastia; small, firm testes; sparse body hair.

From childhood with progression to early puberty, the pituitary-gonadal function observed is within normal limits for 47,XXY males.
At mid puberty and later, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) concentrations rise to hyper-gonadotropic levels, inhibin B levels fall until they are undetectable, and testosterone levels are at low or low-normal levels after an initial increase.

Fragile X syndrome, also termed Martin-Bell syndrome or marker X syndrome, is the most common cause of inherited mental retardation, intellectual disability, and autism.
However, the patient here does not have any mental disabilities as he already works as a clerk, and that too would make Down’s Syndrome less likely.

Classic Kallmann syndrome (KS) and idiopathic hypogonadotropic hypogonadism (IHH) are rare genetic conditions that encompass the spectrum of isolated hypogonadotropic hypogonadism. Most patients have gonadotropin-releasing hormone (GnRH) deficiency, as suggested by their response to pulsatile GnRH therapy. Hypothalamic-pituitary function is otherwise normal in most patients, and hypothalamic-pituitary imaging reveals no space-occupying lesions. By definition, either anosmia or severe hyposmia is present in patients with Kallmann syndrome, in contrast to patients with idiopathic hypogonadotropic hypogonadism, whose sense of smell is normal.

Hashimoto thyroiditis is the most common cause of hypothyroidism in developed countries. In contrast, worldwide, the most common cause of hypothyroidism is an inadequate dietary intake of iodine. This disease is also known as chronic autoimmune thyroiditis and chronic lymphocytic thyroiditis.

European guidelines for the treatment of syndrome of inappropriate antidiuresis include the following recommendations for the management of moderate or profound hyponatremia:
– Restrict fluid intake as first-line treatment.
– Second-line treatments include increasing solute intake with 0.25–0.50 g/kg per day or a combination of low-dose loop diuretics and oral sodium chloride.
– Use of lithium, demeclocycline, or vasopressin receptor antagonists is not recommended.
Recommendations on the treatment of SIADH from an American Expert Panel included the following:
– If chronic, limit the rate of correction.
– Fluid restriction should generally be first-line therapy.
– Consider pharmacologic therapies if serum Na + is not corrected after 24-48 hr of fluid restriction or if the patient has a low urinary electrolyte free water excretion.
– Patients being treated with vaptans should not be on a fluid restriction initially.
– Water, 5% dextrose or desmopressin can be used to slow the rate of correction if the water diuresis is profound.

Primary aldosteronism now is considered one of the more common causes of secondary hypertension (HTN).
Individuals with primary aldosteronism may present with hypokalaemia metabolic alkalosis; however, as many as 38% of patients with primary aldosteronism may be normokalaemia at presentation.
Routine laboratory studies can show hypernatremia, hypokalaemia, and metabolic alkalosis resulting from the action of aldosterone on the renal distal convoluted tubule (DCT) (i.e., enhancing sodium reabsorption and potassium and hydrogen ion excretion).
Plasma aldosterone/plasma renin activity ratio is used for screening because it is fairly constant over many physiologic conditions.

The patient is clinically free, so Cushing diseases can be exclude.

The patient has hyperthyroidism and its most common cause is Grave’s Disease.
Grave’s Disease is an autoimmune disease due to circulating autoantibodies known as TSH receptor stimulating autoantibodies or Thyroid-stimulating immunoglobulins (TSIs) that bind to and activate thyrotropin receptors, causing the thyroid gland to grow and the thyroid follicles to increase the synthesis of thyroid hormone.

Diabetes insipidus (DI) is defined as the passage of large volumes (>3 L/24 hr) of dilute urine (< 300 mOsm/kg). It has the following 2 major forms:
Central (neurogenic, pituitary, or neurohypophyseal) DI, characterized by decreased secretion of antidiuretic hormone (ADH; also referred to as arginine vasopressin [AVP])
Nephrogenic DI, characterized by decreased ability to concentrate urine because of resistance to ADH action in the kidney.
The boy most probably has nephrogenic diabetes insidious (DI) not central DI so he is not responding to the ADH treatment.

The clinical manifestations of Small cell lung cancer (SCLC) can result from local tumour growth, intrathoracic spread, distant spread, and/or paraneoplastic syndromes.
Hypertrophic pulmonary osteoarthropathy (HPO) is a rare paraneoplastic syndrome that is frequently associated with lung cancer; however, the incidence of clinically apparent HPO is not well known.
SIADH is present in 15% of cases and most commonly seen.
Although hypercalcaemia is frequently associated with malignancy, it is very rare in small cell lung cancer despite the high incidence of lytic bone metastases.
Ectopic Cushing’s syndrome in SCLC does not usually exhibit the classic signs of Cushing’s syndrome and Cushing’s syndrome could also appear during effective chemotherapy.
Chemotherapy is the treatment of choice in SCLC.

Hashimoto thyroiditis is part of the spectrum of autoimmune thyroid diseases (AITDs) and is characterized by the destruction of thyroid cells by various cell- and antibody mediated immune processes. It usually presents with hypothyroidism, insidious in onset, with signs and symptoms slowly progressing over months to years.

The diagnosis of Hashimoto thyroiditis relies on the demonstration of circulating antibodies to thyroid antigens (mainly thyroperoxidase and thyroglobulin) and reduced echogenicity on thyroid sonogram in a patient with proper clinical features.

In boys, the first manifestation of puberty is testicular enlargement; the normal age for initial signs of puberty is 9 to 14 years in males. Pubic hair in boys generally appears 18 to 24 months after the onset of testicular growth and is often conceived as the initial marker of sexual maturation by male adolescents.

Exogenous thyroid hormone use has been associated with episodes of thyroid storm as well as thyrotoxic periodic paralysis.
It presents with marked proximal muscle weakness in both upper and lower limbs, hypokalaemia and signs of hyperthyroidism.
Hyperthyroidism generally presents with tachycardia, hypertension, hyperthermia, and cardiac arrhythmias

Laxatives and diuretics can result in electrolyte abnormalities.
Medical complications associated with laxatives include chronic diarrhoea which disrupts the normal stool electrolyte concentrations that then leads to serum electrolyte shifts; acutely, hypokalaemia is most typically seen. The large intestine suffers nerve damage from the chronic laxative use that renders it unable to function properly. The normal peristalsis and conduction are affected; the disorder is thought to be secondary to a degeneration of Auerbach’s Plexi. However, it does not cause muscle weakness.

Insulin tends to cause weight gain, not weight loss.
Metformin does not cause muscle weakness but can cause headaches.

Classic Kallmann syndrome (KS) is due to isolated hypogonadotropic hypogonadism. Most patients have gonadotropin-releasing hormone (GnRH) deficiency, as suggested by their response to pulsatile GnRH therapy. The hypothalamic-pituitary function is otherwise normal in most patients, and hypothalamic-pituitary imaging reveals no space-occupying lesions. By definition, either anosmia or severe hyposmia is present in patients with Kallmann syndrome.

Glucagon-like peptide 1 (GLP-1) is a 30-amino acid peptide hormone produced in the intestinal epithelial endocrine L-cells by differential processing of proglucagon. GLP-1 is released in response to meal intake.
The main actions of GLP-1 are to stimulate insulin secretion (i.e., to act as an incretin hormone) and to inhibit glucagon secretion, thereby contributing to limit postprandial glucose excursions. It also inhibits gastrointestinal motility and secretion and thus acts as an enterogastrone and part of the ileal brake mechanism. GLP-1 also appears to be a physiological regulator of appetite and food intake.
Decreased secretion of GLP-1 may contribute to the development of obesity, and exaggerated secretion may be responsible for postprandial reactive hypoglycaemia.

The patient has primary Hypogonadism.
Since he already had two children, Klinefelter syndrome is excluded and the patient does not need karyotyping.
His lab results are normal indicating normal pituitary gland functions.
So the next step is testicular ultrasound as testicular tumour, infiltration or idiopathic failure is suspected.

Sitagliptin-induced pancreatitis can occur at any time after the initiation of therapy, even after several years. Patients taking sitagliptin who present with signs and symptoms of mild or severe pancreatitis should immediately discontinue sitagliptin and use an alternate medication regimen for control of type 2 diabetes.
In response to pancreatitis reported in post-marketing surveillance through the Adverse Event Reporting System (AERS), the FDA has issued revised prescribing information for sitagliptin stating that cases of acute pancreatitis have been reported with use, to monitor closely for signs and symptoms of pancreatitis, and to use sitagliptin with caution in patients with a history of pancreatitis.

Primary hyperparathyroidism (PHPT) is diagnosed based upon levels of blood calcium and parathyroid hormone (PTH). In most people with PHPT, both levels are higher than normal. Occasionally, a person may have an elevated calcium level and a normal or minimally elevated PTH level. Since PTH should normally be low when calcium is elevated, a minimally elevated PTH is considered abnormal and indicates PHPT.

Prolactinomas, benign lesions that produce the hormone prolactin, are the most common hormone-secreting pituitary tumours.
Based on its size, a prolactinoma can be classified as a microprolactinoma (< 10 mm diameter) or a macroprolactinoma (>10 mm diameter). If the prolactinoma is large enough to compress the surrounding normal hormone-secreting pituitary cells, it may result in deficiencies of one or more hormones (e.g., thyroid-stimulating hormone [TSH], growth hormone [GH], adrenocorticotropic hormone). However, the patient has microadenoma so it is unlikely to cause compression manifestations.
Hyperprolactinemia inhibits GnRH secretion from the medial basal hypothalamus and LH release from the pituitary.