TRT and Fertility: Does Testosterone Cause Infertility?

Spermatogenesis depends on extremely high intratesticular testosterone concentrations — roughly 50–100 times higher than serum levels. These concentrations are produced locally by Leydig cells in response to LH signalling. When exogenous testosterone is administered, the hypothalamus detects adequate (or supraphysiological) androgen levels and reduces GnRH pulsatility, which causes the pituitary to reduce LH and FSH output. Without LH stimulation, intratesticular testosterone production drops, and without FSH, Sertoli cells cease supporting sperm maturation.

The net result: sperm counts typically fall to azoospermic levels (zero sperm) within 3–6 months of starting TRT in men with previously normal fertility. This was first systematically documented in the WHO hormonal contraception studies in the 1980s–1990s, which deliberately used testosterone injections as a male contraceptive — achieving azoospermia in 70–90% of men.

For most men, yes — but recovery takes time and isn't guaranteed. Liu et al. (2006) in the Journal of Clinical Endocrinology & Metabolism followed men after stopping androgen use and found that 67% recovered spermatogenesis within 6 months, 90% within 12 months, and 96% within 24 months. However, recovery was less complete in men who had used TRT for longer durations (>5 years) or at high doses.

Age is also a factor: younger men (under 35) recover more reliably and quickly. Men over 40 who have been on TRT for several years should have a realistic conversation about the probability and timeline of recovery before assuming fertility will return quickly.

Human chorionic gonadotropin (hCG) mimics LH, directly stimulating Leydig cells to maintain intratesticular testosterone production even while exogenous testosterone suppresses pituitary LH. Co-prescribing hCG with TRT (typically 250–500 IU every 2–3 days) maintains testicular size and spermatogenesis in most men. This is the standard approach when fertility preservation is a priority.

FSH co-supplementation (recombinant FSH, used in reproductive medicine) can be added if hCG alone doesn't fully preserve sperm counts — this is more expensive and less commonly used outside fertility clinic contexts.

For men with secondary hypogonadism (low T driven by insufficient LH/FSH signalling, not testicular failure) who want to maintain fertility, enclomiphene citrate is an alternative to exogenous TRT. Enclomiphene is a selective oestrogen receptor modulator (SERM) that blocks oestrogen negative feedback at the hypothalamus and pituitary, increasing GnRH pulsatility and thus LH and FSH — stimulating the testes to produce more testosterone endogenously.

Unlike TRT, enclomiphene does not suppress spermatogenesis — in fact, it may increase sperm parameters. A Phase 3 trial by Wiehle et al. (2014) found that enclomiphene maintained or improved testosterone, LH, FSH, and sperm counts compared to testosterone gel, which suppressed all three. For men with secondary hypogonadism and fertility goals, enclomiphene is often the better first-line option.

If you are starting TRT and are uncertain about future fertility desires, sperm cryopreservation before treatment is a low-cost insurance policy. In Australia, most IVF clinics offer sperm banking for $300–600 per sample with annual storage fees. Given the uncertainty of TRT recovery timelines, this is worth discussing with your treating clinician before the first injection or gel application.

Dr. Nikola Topalovic, MD PhD reviews every FORM client report and specifically discusses fertility status and future plans at the initial assessment — because starting TRT without this conversation is a missed step that can create significant distress for clients who later decide to start a family.

Men on TRT who want to track fertility status should monitor LH and FSH (which will be suppressed — a confirmation that the HPT axis is responding as expected) and, if hCG is co-prescribed, periodic semen analyses every 3–6 months to confirm sperm production is being maintained.

If transitioning off TRT to attempt natural conception, full spermatogenesis recovery may require 6–24 months. During this recovery period, enclomiphene or clomiphene can be used to accelerate HPT axis restart, with LH, FSH, and testosterone monitored at 6–8 week intervals to track progress.