Autoantibodies stimulating the TSH receptor lead to what effect on the thyroid?

• A. Increased thyroid hormone production
• B. Decreased thyroid hormone production
• C. Thyroid destruction via cytotoxic T cells
• D. No effect on thyroid function

Answer: (A)

Stimulating autoantibodies against the TSH receptor act like TSH itself, binding the receptor on thyroid follicular cells and triggering the TSH signaling pathway. This increases iodine uptake and the synthesis and release of thyroid hormones (T3 and T4), often with diffuse thyroid enlargement. Because hormone levels rise, the pituitary lowers TSH via negative feedback. This is the mechanism behind Graves disease, where these antibodies drive hyperthyroidism.

In contrast, decreased hormone production would come from blocking or destruction of thyroid tissue, as seen in other autoimmune thyroid diseases, not from stimulating TSH receptor antibodies.