A 41-year-old woman with Graves' disease presents with temperature 40°C, atrial fibrillation at 150/min, agitation, and free T4 six times the upper limit. Which statement about iodine therapy in this setting is CORRECT?
- A Iodine must be given at least one hour after a thionamide to prevent substrate-driven hormone synthesis ✓
- B Iodine should be the first agent given to achieve rapid hormonal blockade
- C Iodine is contraindicated in thyroid storm because it precipitates cardiovascular collapse
- D Lugol iodine may be used only after total thyroidectomy has been performed
Correct answer: A. Iodine must be given at least one hour after a thionamide to prevent substrate-driven hormone synthesis
Explanation
In thyroid storm, a thionamide such as propylthiouracil is given first to block new hormone synthesis, and iodine is administered at least one hour later. Giving iodine to an untreated gland supplies substrate for synthesis of additional hormone, worsening the crisis. Iodine is a standard component of storm management and is not restricted to postoperative use.
Reference: Williams Textbook of Endocrinology, 14th ed.
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