A patient with Graves disease receives a saturated solution of potassium iodide before thyroidectomy. Within days, her gland becomes firm and hormone synthesis falls, though she later escapes from this effect if iodine is continued. This transient blockade of thyroid hormone release and synthesis is called the:

• A Wolff-Chaikoff effect ✓
• B Jod-Basedow phenomenon
• C Hershberger effect
• D Plummer effect

Explanation

The Wolff-Chaikoff effect is acute inhibition of thyroid peroxidase-mediated organification of iodide by a sudden large iodine load, protecting against iodine-induced thyrotoxicosis. Escape occurs after days when the sodium-iodide symporter downregulates. The Jod-Basedow phenomenon (option B) is the opposite: iodine-induced hyperthyroidism in autonomous nodular glands. Plummer effect refers to iodine unmasking autonomous tissue on scan, and Hershberger relates to androgens.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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