HCG (human chorionic gonadotropin) is a peptide hormone that binds to the same receptor as luteinizing hormone (LH) in the testes. When exogenous testosterone suppresses natural LH production through negative feedback, HCG serves as an LH replacement to keep the testes functioning.
The primary reasons to use HCG alongside TRT are fertility preservation and prevention of testicular atrophy. Exogenous testosterone completely shuts down the HPT axis, causing LH and FSH to drop to near-zero. Without LH stimulation, the Leydig cells stop producing intratesticular testosterone, spermatogenesis declines or ceases, and the testes physically shrink. HCG prevents all three of these outcomes.
Standard dosing for TRT adjunct use is 250-500 IU injected subcutaneously 2-3 times per week. This is sufficient to maintain testicular volume and baseline spermatogenesis in most men. Higher doses (1000+ IU) can stimulate more intratesticular testosterone production but also increase estradiol conversion.
HCG availability has become complicated in the US since the FDA reclassified it as a biologic in 2020, which removed it from compounding pharmacy formularies for a period. Many clinics have since found alternative supply chains, but availability and pricing have been affected. Some practitioners have shifted to alternatives like gonadorelin or enclomiphene for fertility preservation.