Thyroid tissue from a 28-year-old woman with diffuse toxic goiter shows tall columnar follicular cells forming papillary infoldings into lumina, with colloid that appears pale and has scalloped resorption vacuoles at its periphery. The humoral basis of this appearance is:

• A IgG4 antibodies directed against thyroid peroxidase causing follicular destruction
• B IgG antibodies against the TSH receptor that mimic the action of TSH ✓
• C Autoantibodies blocking the TSH receptor and inducing apoptosis
• D Antibodies against sodium-iodide symporter preventing iodine organification

Explanation

In Graves disease, thyroid-stimulating immunoglobulins bind and activate the TSH receptor, driving hypertrophy and hyperplasia of follicular cells with increased hormone synthesis and resorption, producing scalloped colloid. TPO antibodies and TSH-blocking antibodies characterize Hashimoto thyroiditis and atrophic thyroiditis respectively, not hyperthyroidism. The lymphoid infiltrate in Graves represents generalized activation of thyroid antigen-reactive T and A cells.

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.