Fertility & keeping your own production

Testosterone from outside shuts down LH and FSH, so the intratesticular testosterone that sperm production depends on collapses — even though blood levels look great. Around 65% of men reach a zero sperm count within 4–6 months; testosterone has literally been trialled as a male contraceptive. Every major guideline says do not give TRT to a man who wants fertility in the near term. Evidence ●●●●●

The shutdown usually reverses after stopping — roughly 67% recover sperm by 6 months, 90% by a year, and nearly all by two years — but it is slow, variable, and occasionally incomplete, and testicular volume can take longer to return. 'Usually reversible' is not 'guaranteed', which is why it's a decision to make before starting, not after.

Instead of replacing testosterone (which switches the axis off), these stimulate your own. Clomiphene / enclomiphene (a SERM) blocks estrogen's feedback so the brain raises its own LH/FSH — lifting testosterone and preserving sperm (typically ~50 mg a few times weekly, off-label). hCG mimics LH to drive intratesticular testosterone directly (~1,500–3,000 IU two to three times weekly), and FSH (hMG / recombinant FSH) can be added when sperm output needs more. Evidence ●●●●○

For a man who genuinely needs testosterone but wants to protect fertility, adding low-dose hCG (around 500 IU) alongside TRT keeps the testes stimulated, preserving intratesticular testosterone and testicular volume. It's not perfect, but it's far better than replacement alone for anyone hoping to keep the option open.