MRCP2-1157
A 29-year-old woman presents to the Endocrinology Clinic for review. She recently suffered a fall whilst at dancing and was knocked out for a few minutes.
Since then, over the past few weeks, she has suffered polyuria and polydipsia. She has no past medical history of note, and her only medication is the oral contraceptive pill.
On examination, her BP is 125/72 mmHg, with pulse 83/min and regular. She has a postural drop of 15 mmHg on standing. Her BMI is 21. Neurological assessment is unremarkable.
Investigations:
Investigation Result Normal values
Haemoglobin (Hb) 131 g/l 135 – 175 g/l
White cell count (WCC) 8.1 × 109/l 4.0 – 11.0 × 109/l
Platelets (PLT) 191 × 109/l 150 – 400 × 109/l
Sodium (Na+) 146 mmol/l 135 – 145 mmol/l
Potassium (K+) 4.4 mmol/l 3.5 – 5.0 mmol/l
Creatinine (Cr) 142 µmol/l 50 – 120 µmol/l
Urea 9.1 mmol/l 2.5 – 6.5 mmol/l
Glucose 5.4 mmol/l 3.9 – 7.1 mmol/l
Corrected calcium (Ca2+) 2.21 mmol/l 2.2 – 2.7 mmol/l
Which of the following is the most appropriate next investigation?