Glycoprotein hormones [ PUBMED:6267989 PUBMED:1445230 ] (or gonadotropins) are a family of proteins, which include the mammalian hormones follitropin (FSH), lutropin (LSH), thyrotropin(TSH) placental chorionic gonadotropins hCG and eCG [ expand

Glycoprotein hormones [ PUBMED:6267989 PUBMED:1445230 ] (or gonadotropins) are a family of proteins, which include the mammalian hormones follitropin (FSH), lutropin (LSH), thyrotropin(TSH) placental chorionic gonadotropins hCG and eCG [ PUBMED:6314263 ] and chorionic gonadotropin (CG), as well as at least two forms of fish gonadotropins. These hormones are central to the complex endocrine system that regulates normal growth, sexual development, and reproductive function [ PUBMED:6177696 ]. The hormones LH, FSH and TSH are secreted by the anterior pituitary gland, while hCG and eCG are secreted by the placenta [ PUBMED:1713773 ]. All these hormones consist of two glycosylated chains (alpha and beta). The alpha subunit is common to each protein dimer (well conserved within species, but differing between them [ PUBMED:6177696 ]), and a unique beta subunit, which confers biological specificity [ PUBMED:6314263 ]. The alpha chains are highly conserved proteins of about 100 amino acid residues which contain ten conserved cysteines all involved in disulphide bonds [ PUBMED:8202136 ], as shown in the following schematic representation.

 +---------------------------+ +----------+| +-------------|--+ | || | | | xxxxCxCxxxxxxCxCCxxxxxxxxxxxxxCCxxxxxxxxxxCxCxxCx | | | | +------|-----------------+ | | | +----------------------------+'C': conserved cysteine involved in a disulphide bond.

Intracellular levels of free alpha subunits are greater than those of the mature glycoprotein, implying that hormone assembly is limited by the appearance of the specific beta subunits, and hence that synthesis of alpha and beta is independently regulated [ PUBMED:6314263 ].