Thyroid stimulating hormone (TSH), a glycoprotein hormone composed of α and β chains, is produced by thyrotrope cells of the anterior pituitary¹. The TSH receptor (TSHR) plays a prominent role in thyroid physiology and disease. The established biological function of TSHR in the thyroid gland is to regulate synthesis and secretion of thyroid hormones from follicular thyroid cells; it also plays an important role in controlling the growth and development of the thyroid gland².

TSHR is a G-protein coupled receptor and shares the classic structure of the serpentine receptor family (seven membrane spanning segments, an extracellular N-terminus and an intracellular carboxy terminal)³.

TSHR is primarily expressed in the epithelial cells of the thyroid follicles, but TSHR mRNA and protein have been detected in a variety of cell types including brain, testes, kidney, heart, bone, thymus, lymphocytes, adipose tissue and fibroblasts⁴.

Chronic stimulation of the TSHR leads to over activation of the cAMP pathway that in turn causes thyroid hyperplasia and hyperthyroidism. This process occurs in Graves' disease (GD) in which thyroid stimulating antibodies (TSAB) bind the receptor and mimic the action of TSH⁵.