MRCP2-3864
A 36-year-old man presents to the Endocrine Clinic after routine blood testing at the GP surgery. He has no significant previous medical history; his only recent attendance at the doctor’s was for a minor cold. There was no other past history of note and examination revealed blood pressure of 118/78 mmHg. No previous history of hypertension was noted.
Investigations:
Haemoglobin (Hb) 142 g/l 135 – 175 g/l
White cell count (WCC) 7 × 109/l 4.0 – 11.0 × 109/l
Platelets (PLT) 205 × 109/l 150 – 400 × 109/l
Sodium (Na+) 139 mmol/l 135 – 145 mmol/l
Potassium (K+) 2.8 mmol/l 3.5 – 5.0 mmol/l
Bicarbonate (HCO3-) 30 mmol/l 22 – 29 mmol/l
Creatinine (Cr) 95 μmol/l 50 – 120 µmol/l
Which of the following investigations would be most useful in pointing to the diagnosis?