The thyroid hormones, produced by the thyroid gland, are essential for the proper development and differentiation of cells in the body and regulating the metabolism of fats, carbohydrates, and proteins in the body. Production of the thyroid hormone is stimulated by the Thyroid Stimulating Hormone (TSH), which is synthesized in the pituitary. The Thyroid Stimulating Hormone Receptor (TSHR) acts as a bridge between the TSH and the thyroid gland. These receptors, with binding sites for TSH molecules, are situated on the membranes of the follicular cells of the thyroid gland, and serve to act as mediators of the effect of TSH. Once activated by the binding of TSH, the receptor initiates a series of reactions that control the development and functioning of the thyroid gland. Apart from the thyroid, TSHR mRNA has also been detected in other tissues, such as lymphocytes, adipocytes, and neuronal cells. The TSHR protein contains multiple Leucine Rich Repeats (LRRs). Each LRR is coded for by a separate exon and consists of a beta sheet oriented towards the interior of the protein. It is believed that this structure plays a major role in binding the hormone.

Mutations in the TSHR gene have been identified in several people with subclinical hypothyroidism, hyperthyroidism, familial gestational hyperthyroidism, non-autoimmune hyperthyroidism, Grave's disease, and thyrotropin resistance.