What is the clinical significance of TSH receptor antibodies?

• A. They are typically present in Graves' disease and stimulate thyroid hormone production.
• B. They indicate Hashimoto's disease and suppress thyroid function.
• C. They are not related to autoimmune thyroid disease.
• D. They indicate thyroid cancer.

Answer: (B)

TSH receptor antibodies act on the thyroid by targeting the TSH receptor on thyroid follicular cells. When these antibodies are stimulating, as seen in Graves’ disease, they mimic TSH and continuously stimulate the thyroid to produce thyroid hormones, causing hyperthyroidism, diffuse goiter, and related symptoms. This makes their presence a key diagnostic clue for Graves’ disease and explains the hyperthyroid state without requiring TSH levels alone.

In autoimmune thyroiditis like Hashimoto’s, the usual culprits are anti-thyroid peroxidase and anti-thyroglobulin antibodies, which lead to thyroid destruction and hypothyroidism. TSH receptor blocking antibodies can occur but they are not the defining feature of Hashimoto’s and, when present, do not explain Graves’ hyperthyroidism.

TRAb can also cross the placenta, potentially causing fetal or neonatal thyroid dysfunction depending on whether the antibodies stimulate or block the receptor.

So, the clinical significance is that these antibodies, especially the stimulating type, point to Graves’ disease and its tendency to drive excess thyroid hormone production.