Reproductive & sexual-function research
HCG (Human Chorionic Gonadotropin): Research Overview
Pregnancy hormone that acts on the LH receptor. Approved in fertility and hypogonadism medicine.
Also known as human chorionic gonadotropin · choriogonadotropin · Human Chorionic Gonadotropin
What is HCG?
HCG is a glycoprotein hormone naturally produced by the placenta during pregnancy that binds LH receptors to stimulate testosterone and estrogen biosynthesis. FDA-approved for cryptorchidism, hypogonadotropic hypogonadism, and ovulation induction.
What is HCG researched for?
- Maintains intratesticular testosterone at baseline during testosterone therapy, preventing atrophy and preserving fertility.
- FDA-approved for secondary hypogonadism; combined with FSH for spermatogenesis induction.
- Restores testicular function after anabolic steroid cycles.
- FDA-approved trigger for follicular maturation; 15-25% pregnancy rate per cycle.
- FDA-approved for prepubertal undescended testes not due to anatomical obstruction; ~25% success rate.
How does HCG work?
Binds to LH receptors on Leydig cells in testes, stimulating testosterone production with a half-life of 24-36 hours, peak levels 6-12 hours post-injection, and 40-50% bioavailability via SubQ or IM routes.
Reported targets: LH receptor
References
Coviello AD, Matsumoto AM, Bremner WJ, et al. · The Journal of clinical endocrinology and metabolism · 2005
29 men randomized to testosterone enanthate plus 125, 250, or 500 IU HCG every other day. 250 IU maintained intratesticular testosterone within 7% of baseline, preserving fertility potential during TRT.
Controlled clinical trial · PMID 15713727
Madhusoodanan V, Patel P, Lima TFN, et al. · International braz j urol : official journal of the Brazilian Society of Urology · 2019
HCG monotherapy safe and efficacious for hypogonadal symptoms. Erectile dysfunction improved in 86% (19/22), libido in 80% (20/25). No thromboembolic events.
PMID 31408289
Fertility induction in hypogonadotropic hypogonadal men
Prior M, Stewart J, McEleny K, et al. · Clinical endocrinology · 2018
Combined HCG and FSH therapy induces spermatogenesis in 86% (95% CI 82-91%) of men with hypogonadotropic hypogonadism. HCG alone achieves 40% (95% CI 25-56%).
PMID 30194850
Bu Q, Pan Z, Jiang S, et al. · Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme · 2016
Meta-analysis of 13 studies with 872 boys and 1,174 undescended testes. Overall HCG success rate of 24%. Significant effect on bilateral but not unilateral cryptorchidism.
Controlled clinical trial · PMID 27050251
Wei Y, Wang Y, Tang X, et al. · Journal of paediatrics and child health · 2018
Confirmed ~25% success rate for HCG in cryptorchidism treatment. All side effects were transitory and not severe.
Controlled clinical trial · PMID 29655188
Common questions
Why does HCG cause gynecomastia if it just stimulates testosterone?
HCG stimulates testosterone production, but testes also express aromatase enzyme that converts testosterone to estrogen. The increased testosterone availability combined with enhanced intratesticular aromatase activity results in elevated estrogen, causing breast tenderness and gynecomastia. Aromatase inhibitors help prevent this side effect.
What's the success rate of HCG for treating cryptorchidism (undescended testes)?
Meta-analysis of HCG in cryptorchidism shows approximately 24% success rate—modest but clinically relevant for select cases. Success is higher for bilateral versus unilateral cryptorchidism. This low success rate led to surgery becoming the standard treatment for most cases, though HCG remains an initial option.