Which mechanism explains thyrotoxicosis developing in a patient with endemic multinodular goitre shortly after starting amiodarone?

• A TSH receptor stimulating antibodies triggered by iodine load
• B Destructive release of preformed hormone from lymphocytic infiltration
• C Escape from the Wolff-Chaikoff effect due to autonomous nodular tissue ✓
• D Direct cytotoxic effect of iodine on follicular cells

Explanation

This is the Jod-Basedow phenomenon: an iodine load bypasses normal autoregulation in autonomously functioning nodules that cannot sustain the Wolff-Chaikoff inhibition, so unregulated hormone synthesis follows. Amiodarone contains 37% iodine by weight, making it a classic trigger in multinodular goitre. Destructive release describes amiodarone-induced thyroiditis type 2 with a low radioiodine uptake, not autonomous synthesis. TSH receptor antibodies define Graves disease, which is unrelated to the iodine load here.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.