A patient on a longer MDR-TB regimen containing ethionamide together with para-aminosalicylic acid develops fatigue, cold intolerance and a raised TSH after four months. The most likely diagnosis and management are:
- A Drug-induced hypothyroidism; check free T4 and start levothyroxine, continuing anti-TB therapy ✓
- B Isoniazid-induced lupus; stop isoniazid
- C Euthyroid sick syndrome; no action needed
- D Ethambutol-induced adrenal insufficiency; stop ethambutol
Correct answer: A. Drug-induced hypothyroidism; check free T4 and start levothyroxine, continuing anti-TB therapy
Explanation
Ethionamide (and its congener prothionamide) impairs thyroid hormone synthesis, causing goitrous hypothyroidism, and the risk is markedly increased when combined with PAS. Management is thyroid function testing, levothyroxine replacement, and continuation of anti-TB therapy, since stopping these drugs would compromise MDR-TB treatment. Monitoring TSH periodically during regimens containing thioamides is recommended practice.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.