Coming off TRT: restarting your own testosterone.

What TRT does to the axis

Your testosterone is not produced in isolation. The hypothalamus releases GnRH in pulses, which prompts the pituitary to secrete luteinising hormone (LH) and follicle-stimulating hormone (FSH). LH tells the Leydig cells in the testes to make testosterone; FSH, together with a very high local testosterone concentration inside the testis, drives sperm production.¹

When you take testosterone from outside the body, the brain reads the elevated blood level and does the sensible thing: it stops sending the signal. LH and FSH fall, often to undetectable levels. Blood testosterone looks fine — it is being supplied — but the testes are idle. Intratesticular testosterone, which needs to be far higher than blood levels for spermatogenesis to work, collapses.^1,3 This is why testicular volume commonly falls on TRT, and why the sperm count follows.

Suppression of this kind is the expected pharmacology of TRT, and any effective androgen — prescribed replacement or an anabolic steroid cycle — does the same thing to the same loop.²

What "restarting the axis" actually means

A restart unfolds in stages: the exogenous testosterone clears, the hypothalamus and pituitary resume pulsatile GnRH and gonadotrophin release, the Leydig cells respond to returning LH and begin producing testosterone again, and — last, and slowest — spermatogenesis restarts, which alone takes around 70–80 days per cycle of sperm production before anything shows up in a semen analysis.^1,5

Each of those steps can be measured. That is the entire argument for doing this with a physician rather than by feel: LH, FSH, total and free testosterone, estradiol, and semen parameters tell you which step you are stuck on, and a plan that is not working looks completely different at three months from one that simply has not finished yet.

How long does recovery take?

The most precise data on recovery of sperm production after exogenous testosterone come from an unlikely place: hormonal male contraception trials, where healthy men were deliberately suppressed and then followed monthly until they recovered. An integrated analysis of 30 studies and 1,549 men found a median time to a sperm concentration of 20 million/mL of 3.4 months, with a probability of recovery of 67% within 6 months, 90% within 12 months, 96% within 16 months, and 100% within 24 months.⁴

Two honest caveats. First, those were healthy, young, eugonadal men on controlled, relatively short regimens — this is close to a best case. Second, recovery of sperm is not the same as recovery of symptoms: testosterone can come back while a man still feels flat for weeks longer, and vice versa.

Men who used anabolic-androgenic steroids before or instead of prescribed TRT do measurably worse. Greater cumulative exposure predicts slower and less complete recovery, and a meaningful subset of former high-dose users show persistently suppressed testosterone years after stopping.^5,7,8 If that is your history, read our companion piece on recovering hormonal health after anabolic steroids, which covers post-cycle therapy and the AAS-specific evidence in more depth.

The predictors that consistently emerge: longer duration of use, older age, longer-acting testosterone preparations, deeper suppression, and lower baseline sperm concentration all slow recovery down.⁴

Fertility: the part men find out too late

Of the avoidable regrets in this area, this is the most common. Men are started on testosterone in their early thirties, are not asked whether they want children, and return three years later unable to conceive.

The relevant number: about 40% of men on TRT become azoospermic.³ The good news is that this is largely avoidable if it is anticipated. In a study of hypogonadal men treated with testosterone plus low-dose human chorionic gonadotropin (hCG) — which mimics LH and keeps the testes working — semen parameters were maintained over more than a year of follow-up, and no patient became azoospermic.³

So the practical guidance is straightforward:

• Before starting TRT, get a baseline semen analysis and have an explicit conversation about whether you may want children. Sperm banking is cheap relative to the alternative.
• During TRT, if fertility is a live possibility, concurrent low-dose hCG is the evidence-supported way to keep the testes functioning rather than idle.³
• After TRT, if conception is the goal, standard testosterone replacement is counterproductive — it is the thing suppressing sperm production. Restart-directed therapy is a different treatment with a different aim.^1,6

What a medically supervised restart involves

There is no single approved protocol, and anything specific must be individualised by a physician. But the toolkit described in the andrology literature is consistent:^1,5,6

• A baseline and a schedule. LH, FSH, total and free testosterone, estradiol, prolactin, and a semen analysis where fertility matters — repeated at defined intervals rather than whenever symptoms spike. Without serial data you cannot tell recovery from failure to recover.
• Agents that stimulate rather than replace. hCG substitutes for the missing LH signal at the testis; selective estrogen receptor modulators act higher up, at the hypothalamus and pituitary, to raise the body's own LH and FSH output. Both are used off-label in this setting and combination approaches are described for recovery of spermatogenesis.^5,6
• A plan for the gap. Between stopping and recovering, you are functionally hypogonadal — fatigue, low libido, low mood, loss of training performance. This window is predictable, and anticipating it is what stops men from abandoning the attempt.⁸
• Patience measured against data. Given a 70–80 day spermatogenic cycle, a semen analysis repeated at six weeks tells you very little. Timelines need to match the biology.⁵

When coming off is not the right answer

Not every man on testosterone should stop. Some have genuine primary hypogonadism — a testicular problem that was never going to resolve — or organic pituitary disease, and for them replacement is appropriate long-term treatment, not something to be escaped. Endocrine Society guidance is clear that testosterone therapy belongs in men with unequivocally low levels and consistent symptoms, diagnosed on repeated morning measurements before treatment ever starts.²

The men most likely to benefit from a restart attempt are those whose suppression is the consequence of treatment or drug use rather than an underlying testicular failure — and the only way to know which group you are in is a proper diagnostic workup, ideally done before the first prescription.

The wider health picture

Whatever the hormonal decision, coming off is a sensible moment for a broader cardiometabolic assessment. Androgen use — particularly supraphysiologic anabolic steroid use — is associated with adverse cardiovascular effects and unfavourable lipid changes that deserve evaluation on their own terms.⁹ Haematocrit, blood pressure, apolipoprotein B, and glucose metabolism all belong in the same review as LH and FSH.