A patient with obesity who uses thyroxine for weight loss and has normal thyroid function. What histopathologic finding would you expect in the thyroid gland?

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Multiple Choice

A patient with obesity who uses thyroxine for weight loss and has normal thyroid function. What histopathologic finding would you expect in the thyroid gland?

Explanation:
The key idea is that thyroid hormone exerts negative feedback on TSH. When a person takes thyroxine externally, circulating levels rise and the pituitary reduces TSH secretion. Chronic low TSH means less stimulation of the thyroid gland, so the gland progressively shrinks. Histologically, this shows as atrophy: small thyroid follicles with reduced colloid and flattened or attenuated follicular epithelium, and an overall decrease in gland size. Hyperplasia or hypertrophy would reflect increased TSH stimulation, while metaplasia would imply abnormal transformation of tissue—neither applies here.

The key idea is that thyroid hormone exerts negative feedback on TSH. When a person takes thyroxine externally, circulating levels rise and the pituitary reduces TSH secretion. Chronic low TSH means less stimulation of the thyroid gland, so the gland progressively shrinks. Histologically, this shows as atrophy: small thyroid follicles with reduced colloid and flattened or attenuated follicular epithelium, and an overall decrease in gland size. Hyperplasia or hypertrophy would reflect increased TSH stimulation, while metaplasia would imply abnormal transformation of tissue—neither applies here.

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