Glycoprotein hormones alpha chain (CGA)

Glycoprotein hormones alpha chain (CGA) is a shared alpha subunit protein encoded by the *CGA* gene and forms the common component of the four major vertebrate glycoprotein hormones—follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and human chorionic gonadotropin (hCG). These hormones are heterodimers, each composed of the identical CGA alpha subunit and a hormone-specific beta subunit, which determines their physiological specificity. CGA is a secreted, glycosylated cystine-knot protein and is essential for the correct assembly, secretion, and receptor activation by these major hormonal complexes. Biologically, CGA underpins the activity of endocrine axes regulating reproduction, metabolism, and development. Its associated hormones are important in clinical therapy and serve as biomarkers in multiple conditions, notably in reproductive medicine, cancer, and thyroid disease. CGA itself is not a direct drug target but is central to the activity and measurement of its hormone complexes.

Other names

Glycoprotein hormones, alpha polypeptideGlycoprotein hormones alpha chainCGACG-alphaFSH-alphaLSH-alphaTSH-alphaHCGGPHaGPHA1FSHALHATSHAGPA1Anterior pituitary glycoprotein hormones common subunit alphaChoriogonadotropin alpha chainChorionic gonadotrophin subunit alphaFollicle-stimulating hormone alpha chainFollitropin alpha chainLuteinizing hormone alpha chainLutropin alpha chainThyroid-stimulating hormone alpha chainThyrotropin alpha chainfollicle-stimulating hormone alpha subunitchorionic gonadotropin, alpha polypeptideglycoprotein hormones alpha chainCG-ALPHAanterior pituitary glycoprotein hormones common subunit alphachoriogonadotropin alpha chainchorionic gonadotrophin subunit alphaluteinizing hormone alpha chainlutropin alpha chainthyroid-stimulating hormone alpha chainthyrotropin alpha chain

Recombinant or natural hormone drugs act by forming hormone dimers (with the shared alpha chain and hormone-specific beta chain), which bind and activate their cognate G protein-coupled receptors (FSHR, LHR, TSHR, etc.), triggering cAMP signaling cascades and downstream physiological responses. Eltrombopag inhibits ELAVL1/HuR-mediated upregulation of CGA mRNA and protein.