A 35-year-old woman referred for 'generalised anxiety disorder' reports palpitations, heat intolerance, weight loss despite good appetite, fine tremor, and diarrhoea. She has mild proptosis. Before starting an SSRI, which single investigation is MOST appropriate?
- A Serum cortisol at 8 am
- B Serum TSH ✓
- C Random blood glucose
- D Vitamin B12 level
Correct answer: B. Serum TSH
Explanation
The combination of anxiety symptoms with heat intolerance, weight loss despite increased appetite, tremor, diarrhoea, and proptosis points to Graves disease, and suppressed TSH confirms thyrotoxicosis. Treating the thyroid state resolves the anxiety picture, so TSH is the decisive first test. Cortisol screens for Cushing syndrome, which presents with depression rather than hyperadrenergic anxiety. Glucose and B12 do not explain this cluster.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.