A 35-year-old woman presents with palpitations, heat intolerance, weight loss, and bilateral exophthalmos. Thyroid examination reveals a diffusely enlarged, non-tender goiter with an audible bruit. What is the underlying pathogenesis of her condition?

Answer and explanation

Correct answer: C. Thyrotropin receptor stimulating autoantibodies (TRAb)

  1. Step 1: The clinical triad of hyperthyroidism, diffuse non-tender goiter with vascular bruit, and thyroid eye disease (exophthalmos) is diagnostic of Graves' disease.
  2. Step 2: Pathogenesis involves autoantibodies directed against the TSH (thyrotropin) receptor (TRAb / TSI) on thyroid follicular cells, which continuously stimulate cyclic AMP and trigger excessive thyroid hormone synthesis.
  3. Step 3: Identify TSH receptor autoantibodies.
Answer
Thyrotropin receptor stimulating autoantibodies (TRAb).
Why not the others: 'Destruction of follicles by cytotoxic T cells' describes Hashimoto's chronic autoimmune thyroiditis; 'Suppression of iodine organification' describes toxic antithyroid effects; 'Autonomously functioning adenoma' describes toxic multinodular goiter (Plummer's disease) which lacks exophthalmos.

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