In autoimmune thyroid disease like Graves’ disease, which receptor is targeted by stimulating antibodies?

• A. Insulin receptor
• B. HCG receptor
• C. TPO
• D. TSH receptor (TSHR)

Answer: (D)

Autoantibodies that bind and activate the TSH receptor on thyroid follicular cells mimic TSH, chronically stimulating the receptor and driving thyroid hormone production and gland growth. This is what causes the hyperthyroidism and diffuse goiter seen in Graves disease. The stimulating antibodies are often called thyroid-stimulating immunoglobulins and act via the Gs-coupled TSH receptor to raise cAMP and upregulate thyroid hormone synthesis.

Other antibodies like those against thyroid peroxidase are associated with Hashimoto’s thyroiditis and lead to thyroid destruction rather than receptor stimulation, so they don’t explain the hyperthyroidism of Graves.