Thyrotoxicosis is associated with exposure to which trace element?

• A. Iodine
• B. Molybdenum
• C. Selenium
• D. Zinc

Answer: (B)

Excess iodine exposure can precipitate thyrotoxicosis in people who have autonomous thyroid tissue or latent hyperthyroidism. This is known as the Jod-Basedow phenomenon. When a large iodine load reaches the thyroid, it can drive increased synthesis and release of thyroid hormones (T4 and T3) from autonomous nodules, tipping someone into thyrotoxicosis. Normally, the Wolff-Chaikoff effect limits hormone production after a sudden iodine load, but in susceptible individuals the autoregulatory escape doesn’t prevent the excess hormone production, leading to thyrotoxicosis.

Sources of iodine exposure include iodinated contrast media, iodide-containing medications, and high-iodine diets or supplements. The other trace elements listed are not typically associated with triggering thyrotoxicosis through exposure.