HCG

What Is HCG?

HCG is a hormone naturally produced by the placenta during pregnancy, where it helps maintain early pregnancy support. Structurally, it closely resembles luteinizing hormone (LH), a hormone the pituitary gland normally releases to signal the testes to produce testosterone or the ovaries to trigger ovulation.^[1] Because the two hormones bind to the same receptor, HCG can step in and mimic LH's signaling role.

Unlike most compounds on this site, HCG isn't a research-only peptide. It's an FDA-approved medication with a long history of clinical use in fertility treatment and hormone therapy, and it's commonly studied and used alongside testosterone replacement therapy specifically because of its effect on the testes.

What HCG Is Being Researched For

• Testosterone Production

  The central area of HCG research is its ability to activate the same receptor as LH, prompting the testes to continue producing testosterone even when the body's own LH signaling is suppressed.^[1]

• Fertility Preservation During Testosterone Therapy

  Because exogenous testosterone suppresses the body's natural LH signal, researchers have studied whether adding low-dose HCG alongside testosterone therapy can preserve sperm production that would otherwise decline.^[2]

• Male Infertility Treatment

  HCG has also been studied as a standalone or combination treatment for certain forms of male infertility linked to low natural gonadotropin signaling.^[3]

How HCG Works

• Mimicking LH Signaling

  Research points to HCG binding to the same receptor as LH on cells in the testes, called Leydig cells, triggering the same internal signaling cascade that leads to testosterone production. This is why HCG can substitute for the body's own LH signal when that signal is suppressed.^[1]

• Preserving Testicular Function During Suppression

  Research points to a dose-dependent relationship between HCG and testosterone levels measured directly inside the testes. Studies have found that even low doses of HCG, given alongside testosterone therapy, can maintain testicular testosterone levels that would otherwise drop sharply.^[1][2]

Reconstitution and Handling

HCG is typically supplied as a lyophilized powder in a sealed vial and reconstituted with bacteriostatic water before use. Water should be added slowly rather than injected directly into the powder, and the vial should be swirled, not shaken.

Since the amount of water used affects the concentration of the final solution, researchers often use a dosage calculator to work this out before mixing. Once reconstituted, the solution is kept refrigerated to help preserve its stability, and is generally used within a limited window since it degrades once mixed.

Key Takeaways

HCG stands apart from most compounds covered on this site because it's a long-approved medication with decades of clinical use in fertility and hormone therapy rather than a research-only peptide. Its core mechanism centers on mimicking LH to stimulate testosterone production directly in the testes, which is why it's so frequently studied and used alongside testosterone replacement therapy specifically to preserve fertility. Research continues to refine the dosing relationship between HCG and testicular function.

Frequently Asked Questions

Sources and Research

1. Coviello AD, Matsumoto AM, Bremner WJ, et al. Low-Dose Human Chorionic Gonadotropin Maintains Intratesticular Testosterone in Normal Men with Testosterone-Induced Gonadotropin Suppression. J Clin Endocrinol Metab. 2005;90(5):2595-2602.
2. Hsieh TC, Pastuszak AW, Hwang K, Lipshultz LI. Concomitant Intramuscular Human Chorionic Gonadotropin Preserves Spermatogenesis in Men Undergoing Testosterone Replacement Therapy. J Urol. 2013;189(2):647-650.
3. Esteves SC, et al. Human chorionic gonadotropin-based clinical treatments for infertile men with non-obstructive azoospermia. Andrology. 2026.