A 25-year-old woman has diffuse thyrotoxic goiter, exophthalmos, and pretibial myxedema. Histology of the thyroid shows tall columnar follicular cells forming papillary projections into lumina, with pale scalloped colloid. The pathogenetic mechanism is:

• A Autoantibodies stimulating the TSH receptor ✓
• B Autoantibodies blocking the TSH receptor
• C Activating mutation of the TSH receptor gene within follicular cells
• D Germline RET mutation causing C-cell hyperplasia

Explanation

Graves disease is caused by circulating autoantibodies directed against the TSH receptor that stimulate adenylate cyclase, driving hormone synthesis and glandular hyperplasia. The histology reflects this stimulation: tall columnar cells, papillary infolding, and scalloped resorption lacunae in the colloid. Blocking antibodies cause atrophic hypothyroidism, somatic activating TSH receptor mutations cause toxic adenoma rather than ophthalmopathy, and RET mutations underlie medullary carcinoma.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.