Follicle-Stimulating Hormone

TRT suppresses FSH and stops sperm production in most men within 3–6 months. Fertility usually returns within 6–24 months of stopping — but not always, and the data is increasingly mixed on long-term fertility recovery. If kids are on the roadmap, use hCG alongside TRT and bank sperm before starting.

FSH is released by the pituitary gland and drives the testes to produce sperm, acting on the Sertoli cells that support sperm development. It works alongside LH, which handles testosterone production. The adult male reference range is roughly 1.5–12.4 IU/L.

FSH stimulates the Sertoli cells inside the testes, which nurse developing sperm through spermatogenesis. Without adequate FSH signaling, sperm production falls off, even if testosterone is present. This is why FSH is a key marker when evaluating male fertility.

Exogenous testosterone triggers negative feedback that shuts down pituitary FSH (and LH), so sperm production usually crashes within a few months on therapy — making most men temporarily infertile. Men who want to protect fertility while on TRT sometimes use hCG, and low-dose hMG or recombinant FSH may be added to maintain spermatogenesis. These are strategies to discuss with a physician, ideally before starting therapy, and banking sperm beforehand is worth considering.