Endocrine and Reproductive Disorders · USMLE Step 1

A patient with hyperthyroidism has exophthalmos and pretibial myxedema. What is the underlying mechanism?

  1. Fibroblast activation via TSH receptors
  2. Excess cortisol hormone production
  3. Congenital TSH hormone deficiency
  4. Decreased β-adrenergic receptor activity
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Correct answer: Fibroblast activation via TSH receptors

Graves disease involves TSH receptor–mediated fibroblast activation, increasing glycosaminoglycans in the orbit and skin. This causes exophthalmos and myxedema.

Difficulty: Medium Question 13 of 20

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