TSH is the hormone produced by the pituitary gland (small gland at the base of the brain), which is responsible for stimulating the production of T4 and T3 hormones by the thyroid gland. For TSH to stimulate the thyroid gland, it must react with proteins on the surface of thyroid cells called “TSH receptors.”
There are many autoimmune diseases caused by a breakdown in the immune system, where it considers normal proteins in the body as “foreign” and makes antibodies to eliminate them. The immune system can therefore produce proteins against “TSH receptors.” Some of these antibodies will block thyroid gland stimulation, while others, such as TSI (thyroid stimulating immunoglobulin), will uselessly stimulate the thyroid gland, causing hyperthyroidism (excessive production of T4 and T3 hormones). Graves-Basedow disease is an autoimmune hyperthyroidism caused by the presence of these TSH antireceptor antibodies (TRAK). Screening for TSH antireceptor antibodies therefore helps in the differential diagnosis of hyperthyroidism.
A high level of TSH antireceptor antibodies in an individual with signs and symptoms of hyperthyroidism is consistent with autoimmune hyperthyroidism (Graves-Basedow disease).