HCG
A glycoprotein hormone naturally produced during pregnancy, studied for LH-like effects on testicular function, ovulation, and reproductive research.
Molecular Structure
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What is HCG?
Human Chorionic Gonadotropin (HCG) is a glycoprotein hormone naturally produced by the syncytiotrophoblast cells of the placenta during pregnancy. Its primary physiological role is to signal to the maternal corpus luteum to continue producing progesterone during early pregnancy, before the placenta itself takes over progesterone production around weeks 8-12 of gestation. HCG is the hormone detected by pregnancy tests, making it among the most clinically familiar protein hormones in medicine.
HCG is notable in research because it shares the same receptor (LHCGR) as luteinizing hormone (LH) but has approximately 6-fold greater potency and substantially longer half-life. Structurally, HCG is composed of an α subunit (identical to the α subunits of LH, FSH, and TSH) and a β subunit (specific to HCG). HCG products are derived either from the urine of pregnant women (the original source, still used for products like Pregnyl) or produced through recombinant DNA technology (Ovidrel). FDA-approved indications include ovulation induction, treatment of cryptorchidism in male children, and adjunctive therapy in selected cases of hypogonadotropic hypogonadism in men.
Mechanism of action
HCG’s mechanisms of action have been investigated across multiple pathways:
- Luteinizing hormone receptor agonism: HCG binds and activates the LHCGR (luteinizing hormone/choriogonadotropin receptor) expressed on theca cells, corpus luteum, and Leydig cells with approximately 6-fold greater potency than LH itself.
- Effects in females: In females, HCG stimulates corpus luteum function to produce progesterone and is used to trigger the final stage of oocyte maturation and ovulation in assisted reproductive technology cycles, replacing the natural LH surge.
- Effects in males: In males, HCG stimulates Leydig cells to produce testosterone, providing similar signaling to endogenous LH and supporting testicular function and intra-testicular testosterone production.
- Extended half-life through structural features: The 24-amino-acid C-terminal extension of the HCG β subunit (not present in LH) contributes significantly to the substantially longer half-life of HCG compared to LH.
- Pregnancy maintenance signaling: During pregnancy, HCG maintains corpus luteum function for progesterone production during the critical first weeks of gestation, with HCG levels peaking around weeks 8-11 of pregnancy.
These pathways are characterized in extensive human clinical research and preclinical models.
Research applications
HCG has been investigated across several research domains, with the most active areas including:
- Ovulation induction research: HCG is widely used to trigger ovulation in assisted reproductive technology cycles including in vitro fertilization (IVF) and intrauterine insemination (IUI). The use of HCG rather than the natural LH surge is the standard approach in most fertility programs.
- Male hypogonadism research: In men with hypogonadotropic hypogonadism, HCG has been studied to stimulate testicular testosterone production, particularly useful in younger men where preservation of fertility potential is desired, as HCG preserves testicular function unlike exogenous testosterone.
- Cryptorchidism research: HCG has been studied as a non-surgical research approach to undescended testes in pediatric populations, particularly when the testis is in a position where hormonal stimulation might prompt descent.
- Testosterone therapy adjunct research: Men on exogenous testosterone therapy frequently develop testicular atrophy due to suppression of the HPG axis. Research has examined HCG use alongside testosterone to maintain testicular size and intra-testicular testosterone production.
- Comparative gonadotropin research: HCG has served as a research reference for studying LHCGR pharmacology and the effects of sustained versus pulsatile gonadotropin signaling on reproductive function.
This compound is intended for laboratory research use only. It has not been approved for human therapeutic use by any regulatory agency.
Storage & reconstitution
In its lyophilized form, HCG should be stored at 2-8°C protected from light. Some recombinant products have different storage requirements per manufacturer specifications. Properly stored lyophilized peptide remains stable for 24 months or longer.
Once reconstituted with bacteriostatic water or sterile water for injection, HCG solutions should be stored refrigerated at 2-8°C and used within 30-60 days depending on formulation. Avoid repeated freeze-thaw cycles, which can degrade peptide structure and reduce activity.
Visual inspection should be performed before each use. The reconstituted solution should be clear and colorless. Reject any solution that appears cloudy, discolored, or contains visible particulate matter.
For step-by-step reconstitution calculations, see our reconstitution calculator.
For laboratory research use only. The compound described on this page is intended exclusively for in vitro research and laboratory experimentation by qualified researchers and is not for human or veterinary use. It is not a drug, food, dietary supplement, or cosmetic, and has not been approved by the FDA, Health Canada, EMA, or any other regulatory authority for the diagnosis, treatment, cure, mitigation, or prevention of any disease or medical condition. The information provided on this page is for educational and reference purposes only and does not constitute medical advice. By accessing this content you confirm that you are a qualified researcher purchasing for legitimate laboratory purposes.