What Is HCG?
Human Chorionic Gonadotropin (HCG) is a 237-amino-acid glycoprotein hormone naturally produced by syncytiotrophoblast cells of the placenta during pregnancy. Structurally related to LH, FSH, and TSH — all sharing an identical α-subunit and differing only in their β-subunits — HCG's similarity to LH allows it to bind and activate the LH/HCG receptor on Leydig cells in the testes with high affinity.
Primary Research Functions
HCG stimulates Leydig cells to produce testosterone, making it central to research on hypogonadism, testosterone replacement, and fertility support. Unlike exogenous testosterone, which suppresses the HPG axis and reduces endogenous LH signaling, HCG provides direct LH-like stimulation at the testicular level without pituitary suppression of downstream gonadotropins.
Gonadal Preservation Research
A prominent area of HCG research involves co-administration with testosterone therapy to maintain testicular size, function, and intratesticular testosterone concentrations — the latter being essential for spermatogenesis even when systemic testosterone levels are adequate. Studies show HCG effectively preserves sperm parameters and testicular volume during androgen protocols.
Female and Fertility Applications
In female fertility research, HCG serves as an LH surrogate that triggers ovulation during controlled ovarian stimulation cycles and as the ovulation-triggering agent in IVF protocols after follicle maturation.
Quick Reference
Member reference tables summarize the compound's research parameters.
Research Indications
Research Protocols
As reported in cited literature and research-community logs (see Research Citations below), not a personal dosing recommendation.
This member section describes parameters reported in the research literature.
Peptide Interactions
This member section summarizes reported compound interactions and evidence limitations.
Reported Research Time Points
This member section summarizes reported research time points.
Safety Notes
Included for harm-reduction awareness only, in the event this compound is encountered outside its labeled research use. Inclusion here does not imply RUO Codes endorses, recommends, or instructs human use.
This member section discusses research safety considerations and uncertainties.
Quality Indicators
Research Citations
- Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression
Coviello AD, Matsumoto AM, Bremner WJ, et al., 2005, J Clin Endocrinol Metab - Age and duration of testosterone therapy predict time to return of sperm count after human chorionic gonadotropin therapy
Kohn TP, Louis MR, Pickett SM, et al., 2017, Fertil Steril - Management of endocrine disease: reversible hypogonadotropic hypogonadism
Dwyer AA, Raivio T, Pitteloud N, 2016, Eur J Endocrinol - Biological functions of hCG and hCG-related molecules
Cole LA, 2010, Reprod Biol Endocrinol - A short evolutionary history of FSH-stimulated spermatogenesis
Huhtaniemi I, 2018, Hormones (Athens) - HCG Diet Products Are Illegal
FDA, 2011, FDA Consumer Update - Exogenous testosterone: a preventable cause of male infertility
Crosnoe LE, Grober E, Ohl D, Kim ED, 2013, Transl Androl Urol - Recombinant versus urinary-derived hCG for ovulation induction
Hershlag A, Peterson CM, 2003, Fertil Steril