Testosterone and TRT — Body Handbook

Healthcare · §665

Testosterone and TRT

Most men diagnosed with "low T" never had it confirmed properly: one afternoon blood draw, a number under some lab's line, a gel prescription within the week. The number swings 20–25% across a single day and drops another quarter after a meal, and about one man in three whose first reading lands low tests normal on a repeat morning draw Bhasin et al. 2018. Test properly, find the cause, and most of these men turn out not to need testosterone at all.

Decide · As-needed Evidence Moderate Chapter Healthcare

Testosterone is not a number. It is the end of a chain: brain signals the pituitary, pituitary signals the testicles, testicles make testosterone. Measuring it alone tells you almost nothing. You need the pituitary's messenger hormones drawn at the same time to know what caused the low reading ¹.

Where it helps, it helps modestly. In men 65 and older with confirmed low testosterone, a year of gel improved libido, sexual function and mood a moderate amount, and did nothing for vitality or thinking ². In at-risk men it did not raise heart attacks or strokes, but did raise atrial fibrillation, blood clots and fractures ³ ⁴. It does not prevent heart disease or dementia.

Starting it is a lifelong commitment. Exogenous testosterone tells the brain the testicles are fine, so your own production shuts down within weeks and fertility with it ⁵. Stop, and symptoms rebound within weeks to worse than where you began. Most "age-related" decline in middle-aged men is really obesity-related, and reversible ⁶. Testing properly costs almost nothing. Starting when you did not need to costs you fertility and your unmedicated baseline for good.

Do not treat a single number. Confirm it, find the cause, fix what is fixable, then decide.

Draw blood twice, both between 07:00 and 10:00, fasted, no coffee. One morning value is not a diagnosis; repeat on a different morning if the first is low ¹.
Order luteinising hormone, FSH, prolactin and SHBG on the same draw. High LH and FSH point to the testicle; low or normal point upstream to weight, opioids, sleep apnoea or a pituitary problem.
Insist on symptoms that fit: dropped libido, fewer morning erections, erectile dysfunction. Fatigue and low mood alone are too vague to carry the call.
Fix the reversible drivers first. Losing about 10% of body weight recovers roughly 84 ng/dL ⁶; treating sleep apnoea and tapering opioids recover more ⁷.
Only then decide. Confirmed low morning testosterone, real symptoms, a known cause and no fertility plans make a reasonable conversation. Missing any one, address that first.

If you want children, there is another path. Clomiphene or enclomiphene nudge the pituitary to send more signal, so the testicles make their own testosterone and keep producing sperm ⁸. A man who loses 30 pounds, treats his apnoea and drops his opioid dose can recover enough to need no prescription at all ⁶.

When the diagnosis is real, the arc is moderate. Weeks one to four: morning erections return, the afternoon-flat feeling lifts. Months two and three: sex drive comes back in a way a partner notices, mood shifts slightly ². Months six to twelve: a small gain in lean mass, a small drop in waist fat, less than a year of lifting would do. The dramatic before-and-after the clinics advertise is not what the trials found.

The fine print — when to skip it, and what people get wrong

"My lab said I'm low." Commercial labs set the floor around 240–250; the clean-cohort guideline number is 264 ng/dL, so a 350 is genuinely borderline and a 250 is not clearly low ¹. "TRT won't hurt fertility." It collapses sperm production within weeks; freeze a sample first ⁵.

Do not start with active prostate or breast cancer, an unevaluated PSA above 4, a haematocrit above 48%, a recent clot, untreated severe sleep apnoea, unstable heart disease, or a wish to conceive soon ¹. If started, monitor testosterone, haematocrit and PSA at 3 and 6 months, then yearly.

References

1Bhasin S, Brito JP, Cunningham GR, Hayes FJ, Hodis HN, Matsumoto AM, Snyder PJ, Swerdloff RS, Wu FC, Yialamas MA (2018). Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. link
2Snyder PJ, Bhasin S, Cunningham GR, Matsumoto AM, Stephens-Shields AJ, Cauley JA, Gill TM, Barrett-Connor E, Swerdloff RS, Wang C, Ensrud KE, Lewis CE, Farrar JT, Cella D, Rosen RC, Pahor M, Crandall JP, Molitch ME, Cifelli D, Dougar D, Fluharty L, Resnick SM, Storer TW, Anton S, Basaria S, Diem SJ, Hou X, Mohler ER 3rd, Parsons JK, Wenger NK, Zeldow B, Landis JR, Ellenberg SS (2016). Effects of Testosterone Treatment in Older Men. New England Journal of Medicine. link
3Lincoff AM, Bhasin S, Flevaris P, Mitchell LM, Basaria S, Boden WE, Cunningham GR, Granger CB, Khera M, Thompson IM, Wang Q, Wolski K, Davey D, Kalahasti V, Khan N, Miller MG, Snabes MC, Chan A, Dubcenco E, Li X, Yi T, Huang B, Pencina KM, Travison TG, Nissen SE (2023). Cardiovascular Safety of Testosterone-Replacement Therapy. New England Journal of Medicine. link
4Snyder PJ, Bauer DC, Ellenberg SS, Cauley JA, Buhr KA, Bhasin S, Miller MG, Khan NS, Li X, Nissen SE (2024). Testosterone Treatment and Fractures in Men with Hypogonadism. New England Journal of Medicine. link
5Coviello AD, Matsumoto AM, Bremner WJ, Herbst KL, Amory JK, Anawalt BD, Sutton PR, Wright WW, Brown TR, Yan X, Zirkin BR, Jarow JP (2005). Low-Dose Human Chorionic Gonadotropin Maintains Intratesticular Testosterone in Normal Men with Testosterone-Induced Gonadotropin Suppression. Journal of Clinical Endocrinology & Metabolism. link
6Camacho EM, Huhtaniemi IT, O'Neill TW, Finn JD, Pye SR, Lee DM, Tajar A, Bartfai G, Boonen S, Casanueva FF, Forti G, Giwercman A, Han TS, Kula K, Keevil B, Lean ME, Pendleton N, Punab M, Vanderschueren D, Wu FC (2013). Age-associated changes in hypothalamic-pituitary-testicular function in middle-aged and older men are modified by weight change and lifestyle factors: longitudinal results from the European Male Ageing Study. European Journal of Endocrinology. link
7Kafel S, Braga-Basaria M, Basaria S (2025). Opioid-induced androgen deficiency in men: Prevalence, pathophysiology, and efficacy of testosterone therapy. Andrology. link
8Krzastek SC, Smith RP (2020). Non-testosterone management of male hypogonadism: an examination of the existing literature. Translational Andrology and Urology. link

Related in the handbook (12)

Alternatives

— Before committing to lifelong TRT, tongkat ali is a gentler option that nudges low-normal testosterone back up.

— If you might want children, get this baseline before any testosterone therapy, which switches off your own production.
— Low testosterone quietly weakens bone; men found low should ask about a bone-density scan before age compounds the loss.
— Before chasing testosterone boosters like boron, find out whether your level is actually low.
— New ED makes men suspect low testosterone, but it's more often a blood-flow warning — confirm the cause before reaching for TRT.
— Gynecomastia can be driven by the hormone shifts TRT causes, so the testosterone decision is part of this picture.
— Low T is the classic case of a borderline lab driving a lifelong decision. Confirm it on two fasted morning draws first.
— Lost morning erections can point to low testosterone as well as vascular trouble; check both before deciding on treatment.
— Men with Peyronie's disease more often run low on testosterone, one more reason a level can be worth checking.
— Starting testosterone means a PSA check first and follow-up tracking, since the prostate is the main organ to keep an eye on.
— Sleep apnea quietly drags testosterone down; treating the apnea can raise it without ever needing TRT.
— A varicocele can quietly drag testosterone down, which is worth checking before assuming you need TRT.