A 60-year-old man from a coastal goitre-endemic region receives iodised salt supplementation for the first time. Within weeks he develops tremor, weight loss, and a suppressed TSH with an autonomous nodular goitre. What is the underlying mechanism?
- A Escape from the acute inhibitory effect of iodide on hormone release by normal follicular cells
- B Autonomous thyroid tissue synthesising excess hormone when iodine supply becomes abundant, independent of TSH control ✓
- C Loss of the Wolff-Chaikoff effect leading to destructive release of preformed hormone
- D Iodine-triggered production of thyroid-stimulating immunoglobulins in susceptible individuals
Correct answer: B. Autonomous thyroid tissue synthesising excess hormone when iodine supply becomes abundant, independent of TSH control
Explanation
This is the Jod-Basedow phenomenon: nodules with autonomous function lose normal TSH regulation and overproduce hormone as soon as adequate iodine becomes available. The Wolff-Chaikoff effect describes the opposite response, physiological suppression of organification by excess iodide, seen in normal glands. No immune stimulation or destructive release is involved in Jod-Basedow thyrotoxicosis.
Reference: Williams Textbook of Endocrinology, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.