A 34-year-old woman with known Graves disease presents with fever of 40 degrees C, heart rate 148 with an irregularly irregular pulse, delirium, and diarrhoea. She is to be treated with a beta blocker, an antithyroid drug, and iodine. Which antithyroid drug is preferred at this stage?
- A Methimazole
- B Potassium perchlorate
- C Propylthiouracil ✓
- D Radioiodine ablation
Correct answer: C. Propylthiouracil
Explanation
Propylthiouracil uniquely inhibits peripheral conversion of T4 to T3 in addition to blocking thyroidal hormone synthesis, making it the preferred agent in thyroid storm where rapid reduction of circulating T3 matters. Methimazole blocks synthesis only. Iodine is given about one hour after the thionamide so that newly synthesised hormone is not fuelled. Radioiodine is absolutely contraindicated in storm because radiation thyroiditis can release stored hormone and worsen the crisis.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.