Hormone chemistry, volume 1: Protein, polypeptide and peptide hormones: by W. R. Butt, second edition, published by Halstead (Wiley) New York-London, 1975. £12.50 (xiv+272 pages)

Abstract

The thyroid-stimulating hormone receptor (TSHR), luteinizing hormone receptor (LHR), and follicle-stimulating hormone receptor (FSHR) are collectively referred to as the glycoprotein hormone receptors because they bind the structurally similar glycoprotein hormones. The glycoprotein hormones consist of the pituitary hormones thyroid-stimulating hormone (thyrotropin, TSH), luteinizing hormone (lutropin, LH), and follicle-stimulating hormone (follitropin, FSH) as well as the placental hormone, chorionic gonadotropin (choriogonadotropin, CG). The glycoprotein hormones are each composed of two dissimilar subunits (α and β) that are noncovalently associated. Within a given species, the α-subunit is identical and the β-subunits are distinct but homologous. Due to the nearly identical nature of LHβ and CGβ, the LHR binds either LH or CG. The binding specificity of LH/CG to the LHR, FSH to the FSHR, and TSH to the TSHR is fairly strict. However, in some cases, extremely high levels of hormone can cause activation of the inappropriate receptor. Because the LHR and FSHR are localized primarily to the gonads, these two receptors are also referred to as the gonadotropin receptors. The glycoprotein hormone receptors belong to the family A (rhodopsin-like) group of G-protein-coupled receptors (GPCRs). However, they share the relatively unique feature of having large extracellular domains that mediate the high affinity binding of hormone. In spite of their different physiological roles, the glycoprotein hormone receptors share a similar structural organization and mechanism of action.