Educational reference, not medical advice. This page summarizes information from published research and regulatory filings for educational purposes. It is not a recommendation to use any compound and should not replace guidance from a licensed healthcare provider. Most peptides discussed here are not approved for the uses described.
What it is
Human chorionic gonadotropin (hCG) is a glycoprotein hormone — strictly speaking, not a peptide. It is a heterodimer of two subunits: an alpha subunit shared with luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone, and a beta subunit that is unique to hCG and provides receptor specificity. Together the protein has 237 amino acids and a molecular mass of roughly 36.7 kDa, far larger than the short peptides covered elsewhere in this library.
It is included here because injectable hCG is widely used alongside peptide protocols in men's health and fertility settings, and because the dosing conventions (international units rather than milligrams) and reconstitution mechanics share the workflow even if the chemistry does not.
History
The hormone was discovered in 1927 by Selmar Aschheim and Bernhard Zondek as the substance in pregnant urine responsible for the original immunological pregnancy test (the "Aschheim-Zondek reaction"). Urinary-derived hCG entered clinical use in the 1930s and 1940s and was among the first hormone preparations to support assisted reproduction. The first FDA approvals for the modern urinary-derived products date to the 1950s and 1960s.
Recombinant choriogonadotropin alfa (Ovidrel) was approved by the FDA in 2000, providing a non-urinary-derived alternative with consistent potency. Urinary-derived Pregnyl (Organon) and Novarel are still available; both are extracted and purified from pooled urine of pregnant women.
Regulatory status
FDA approved for three indications. In women: induction of ovulation in selected anovulatory infertility, typically after FSH-driven follicular development. In men: stimulation of testosterone production in selected cases of hypogonadotropic hypogonadism. In children: treatment of prepubertal cryptorchidism not due to anatomic obstruction.
The FDA does not approve hCG for weight loss, and has stated that over-the-counter hCG products marketed for weight loss are "fraudulent and illegal." Homeopathic hCG products marketed for the same purpose are prohibited. The TRT-adjunct use of hCG in men — to maintain endogenous testosterone production and testicular size during exogenous testosterone administration — is widely practiced but off-label.
Mechanism
hCG binds the LH/CG receptor on Leydig cells (testes) and theca and granulosa cells (ovaries) with affinity comparable to luteinizing hormone itself. Because circulating hCG has a half-life of more than a day compared with LH's half-life of around 20 minutes, exogenous hCG delivers substantially more total LH-receptor stimulation per dose than a comparable amount of LH would.
In men, this drives Leydig cell production of testosterone and the early steps of spermatogenesis. In women undergoing ovulation induction, a single trigger dose produces the LH surge that completes oocyte maturation and triggers ovulation. The mechanism is the same in both sexes; the indications differ.
Half-life and dosing intervals
Published terminal half-life of subcutaneous or intramuscular urinary-derived hCG is approximately 36 hours. Recombinant Ovidrel has a similar half-life of roughly 33 hours. The long half-life relative to native LH is what makes hCG useful clinically — a single injection produces a sustained signal.
Dosing is in international units (IU), not milligrams. Approved protocols vary widely:
- Ovulation trigger (women): 5,000 to 10,000 IU urinary hCG, or a single 250 mcg dose of Ovidrel, given intramuscularly or subcutaneously.
- Male hypogonadotropic hypogonadism: Typically 1,000 to 4,000 IU two to three times weekly subcutaneously or intramuscularly.
- Cryptorchidism: Pediatric weight-based protocols, typically 500 to 1,500 IU per dose for several weeks.
- TRT-adjunct (off-label): Commonly 250 to 500 IU two to three times weekly subcutaneously.
Reconstitution example
Pregnyl and Novarel ship as a lyophilized powder vial paired with a diluent vial of bacteriostatic water; the manufacturer-supplied diluent is the standard reconstitution. A 5,000 IU vial reconstituted with 5 mL of bacteriostatic water yields 1,000 IU/mL. On a 1 mL U-100 insulin syringe, 25 units (0.25 mL) delivers 250 IU, and 50 units (0.5 mL) delivers 500 IU. Vial's calculator handles the IU-to-volume conversion when vial potency and water volume are entered. Ovidrel ships pre-filled at a fixed 250 mcg dose and does not require reconstitution.
What to know
- Not technically a peptide. hCG is a 237-amino-acid glycoprotein hormone. It is included here because of the overlap with peptide protocols, not the chemistry.
- Dosed in IU, not mg. International units measure biological potency. Direct mg-to-IU conversion is not meaningful across preparations.
- Weight loss claims are not approved. The FDA has stated that hCG is not effective for weight loss and that over-the-counter hCG weight-loss products are illegal.
- Common reported side effects: injection-site pain, headache, gynecomastia (in men, dose-dependent), ovarian hyperstimulation syndrome (in women receiving high trigger doses).
- Cardiac and prostate considerations. Long-term use in adult men should account for hematocrit, prostate-specific antigen, and cardiac status as with any androgen-promoting therapy.
- Storage. Lyophilized: refrigerate, protect from light. Reconstituted: refrigerate; urinary-derived hCG is stable for roughly 60 days under refrigeration per the Pregnyl label, though some clinicians use a shorter window.
- Distinct from gonadorelin. Gonadorelin acts on the pituitary to drive endogenous LH; hCG bypasses the pituitary and acts directly at the gonad. They are sometimes substituted for each other in TRT-adjunct practice but operate at different points in the axis.
Sources
- 1.Fink J et al. (2021). Human chorionic gonadotropin treatment: a viable option for management of secondary hypogonadism and male infertility. Expert Review of Endocrinology & Metabolism.
- 2.Alexander EC et al. (2024). Gonadotropins for pubertal induction in males with hypogonadotropic hypogonadism. European Journal of Endocrinology.
- 3.FDA Consumer Update — HCG Diet Products Are Illegal.
- 4.Habous M et al. (2018). Clomiphene citrate and human chorionic gonadotropin are both effective in restoring testosterone in secondary hypogonadism. BJU International.