Answer to Question #61987 in Human Anatomy and Physiology for Sanjukta Ghosh

Question

How are Thyroid Stimulating Ab destroying thyroid tissues?
I was reading Graves' disease which is an autoimmune disorder. I read few books that includes Endocrinology by Hadley and Levine and websites where they mention that antibodies named TSAb (Thyroid stimulating Antibodies) bind to TSH receptors and stimulates synthesis and release of thyroid hormones from thyroid gland. This results into the symptoms of Exopthalmic goitre or graves' disease.
Now my question is how are these antibodies actually attacking the healthy tissues(which I presume is the tissue of thyroid gland)?
I've so far found no website explaining this part of the autoimmune disorder. I'd appreciate any information or references in this regard.

Answer 1

Thyroid stimulating antibodies (sTRAb) don't destroy thyroid tissue. To the contrary, they have a TSH-like effect on thyrocytes and therefore lead to hyperthyroidism and thyroid growth resulting in goiter. The exception is Graves' disease with Hashimoto component. Here, the thyroid is also affected by cytotoxic T cells and antibodies directed against thyroid peroxidase, which gives rise to destruction of the thyroid. But even in this case, it aren't the sTRAb, which destroy tissue.
Perhaps healthy tissues refers to extrathyroidal tissues. Due to unknown reasons several tissues including skeletal muscle, heart muscle, adipose tissue and skin have TSH receptors, and they are affected by sTRAb, too. Hypertrophy results from cross-talk of TSH receptors with IGF-1 receptors in Graves' disease.