Human Chorionic Gonadotropin (HCG)

• HCG maintains the corpus luteum and stimulates progesterone production during early pregnancy, which maintains the endometrial lining, inhibits uterine contractions and supports early embryo development.
• HCG promotes ovulation and egg maturation in fertility treatments.
• HCG stimulates Leydig cells in males to produce testosterone, leading to the development of secondary sexual characteristics in males and the maintenance of spermatogenesis (with additional support from FSH acting on Sertoli cells).

HCG binds to the Luteinizing Hormone/Chorionic Gonadotropin Receptor (LHCGR) (a G-protein-coupled receptor, GPCR) on ovarian or testicular cells. Upon binding to LHCGR, HCG induces a conformational change in the receptor, which activates the HCG alpha subunit of the associated heterotrimeric G-protein. This, in turn, stimulates the enzyme adenylate cyclase, which converts ATP to cyclic AMP (cAMP). The increase in intracellular cAMP acts as a second messenger to activate protein kinase A (PKA). Activated PKA phosphorylates various downstream target proteins, including transcription factors that regulate gene expression of steroidogenic enzymes and enzymes involved in cholesterol mobilization and transport. The net effect is the initiation and amplification of steroid hormone synthesis.

The synthesis of the steroid hormone triggers the following female ovarian functions:

• In granulosa and theca cells of the ovary, cAMP/PKA signaling upregulates enzymes like: CYP11A1 (cholesterol side-chain cleavage enzyme), 3β-HSD (3β-hydroxysteroid dehydrogenase) and CYP19A1 (aromatase, especially important in estrogen synthesis). This leads to the production of progesterone, estrogen, and androgens.
• The surge of HCG (as a mimic of LH) promotes oocyte maturation (resumption of meiosis), follicular rupture and ovulation. Luteinization of the ruptured follicle into the corpus luteum, which continues producing progesterone to support implantation and early pregnancy.

In the males Leydig cells, LHCGR activation by HCG leads to upregulation of enzymes involved in testosterone biosynthesis from cholesterol, specifically, enzymes like CYP11A1, 17β-HSD, and CYP17A1. The resulting testosterone supports spermatogenesis (indirectly via Sertoli cell support), stimulates secondary sexual characteristics and reproductive organ development.

• Reproductive biology studies – follicle development, corpus luteum function.
• Used in studies of assisted reproductive technology (ART) protocols.
• Tumor marker research – HCG as a biomarker in testicular cancer, choriocarcinoma, and gestational trophoblastic diseases.
• Endocrinology research – investigating gonadotropin signaling, feedback mechanisms.
• Weight loss and metabolic studies.

• Available as white to almost white lyophilized powder
• Store in a sterile, airtight, tamper-proof container, at a temperature of 2-8 °C