A patient starts a large iodide load as part of preoperative preparation for thyroidectomy. Within 48 hours, thyroid hormone synthesis falls sharply. Which phenomenon explains this acute fall?
- A Wolff-Chaikoff effect ✓
- B Jod-Basedow phenomenon
- C Iodide-induced stimulation of thyroid peroxidase
- D Increased TSH secretion from the pituitary
Correct answer: A. Wolff-Chaikoff effect
Explanation
The Wolff-Chaikoff effect is an autoregulatory protective response in which a sudden rise in intracellular iodide transiently inhibits organification and thyroid hormone synthesis. It develops within 24 to 48 hours and normally escapes after several days. The Jod-Basedow phenomenon is the opposite event, where iodide excess induces hyperthyroidism in autonomous thyroid tissue, which eliminates option B. TSH secretion falls, not rises, when thyroid hormone output is briefly maintained.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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