HCG (Human Chorionic Gonadotropin)

Human chorionic gonadotropin (HCG) is a glycoprotein hormone composed of two subunits: alpha (shared with LH, FSH, and TSH) and beta (unique to HCG). It's produced in massive quantities during pregnancy by the placenta, which is where pharmaceutical HCG was historically sourced. Modern recombinant versions are also available. In men's health, HCG found its role as the answer to a fundamental problem with testosterone replacement therapy. When a man takes exogenous testosterone, the hypothalamus detects high circulating levels and shuts down GnRH secretion. Without GnRH, the pituitary stops producing LH and FSH. Without LH, the Leydig cells in the testes go dormant. The result: testicular atrophy, near-zero intratesticular testosterone, and cessation of sperm production. HCG fixes this by replacing the missing LH signal. It binds to the same receptor on Leydig cells and tells them to keep producing testosterone locally. A 2005 study by Coviello et al. in JCEM (PMID: 15562008) measured intratesticular testosterone directly and found that 250 IU every other day maintained ITT at about 25% of baseline. Without HCG, ITT dropped to near-zero levels. That 25% is enough to support basic spermatogenesis in most men. The standard TRT protocol includes HCG at 250-500 IU two to three times per week, injected subcutaneously. This keeps testicular volume stable (preventing the shrinkage that bothers many TRT patients) and maintains the intratesticular hormonal milieu needed for sperm production. A 2013 study in Fertility and Sterility (PMID: 23548942) showed that 500 IU three times weekly preserved spermatogenesis in 67% of men on concurrent TRT over 12 months. Beyond fertility, HCG maintains intratesticular production of pregnenolone and DHEA, neurosteroids that may contribute to the improved well-being some men report when adding HCG to their TRT protocol. This "feel better" effect is anecdotal but consistently reported in clinical settings. HCG's regulatory history got complicated in 2020 when the FDA reclassified it from a drug to a biologic under the BPCI Act. This temporarily disrupted compounding pharmacy access, as biologics face different compounding rules than traditional drugs. After significant pushback from the TRT community and compounding industry, access through 503B outsourcing facilities was restored, though the landscape remains more complex than it was pre-2020. Storage requirements matter: reconstituted HCG should be refrigerated at 2-8C and used within 30-60 days, depending on the formulation. Lyophilized (powder) HCG is stable at room temperature before reconstitution. Reconstitute with the bacteriostatic water provided, drawing it slowly down the side of the vial. Side effects primarily relate to estradiol elevation. HCG stimulates intratesticular aromatase, converting some of the locally produced testosterone to estradiol. In men who are already aromatizing heavily from their TRT dose, adding HCG can push estradiol high enough to cause water retention, mood changes, or gynecomastia. Monitoring estradiol levels 4-6 weeks after starting HCG is standard practice.