Few interventions in men’s health are marketed as aggressively as testosterone. Clinics advertise energy, strength, libido, and something close to youth itself, and the pitch lands on an audience of men over 40 who are tired for ordinary reasons. Underneath the marketing there is a real therapy with a real evidence base. The problem is that the evidence base is bounded, and the marketing is not. For clinicians, the useful work is drawing the boundary precisely.
Start with the diagnosis
The Endocrine Society guideline is unambiguous about what a diagnosis requires: symptoms consistent with deficiency, and two morning testosterone measurements below the reference range, drawn on separate days. Morning matters because levels peak early and fall through the day; a 4 p.m. value can manufacture a deficiency that a 8 a.m. value would not confirm. Sleep apnea, obesity, acute illness, and several common medications suppress levels transiently, and each is a reason to repeat testing rather than to start treatment.
A meaningful share of men now on therapy never met those criteria. That is not a gray zone. Treatment without a confirmed diagnosis exposes a man to the full risk ledger in exchange for benefits the trials never measured in men like him.
What the trials support
In men with confirmed deficiency, the supported benefits are specific. Sexual function improves, modestly and consistently. Anemia of unexplained cause corrects in a substantial fraction of treated men. Bone mineral density increases. Effects on energy, mood, and cognition are smaller, inconsistent across trials, and easily confounded by expectation in a therapy men can often feel.
What the trials do not support is treatment of age itself. Men with normal levels and no symptoms were not the population studied, and raising a normal number toward the top of the range is an intervention without an evidence base, whatever the clinic brochure says.
The risk ledger
Cardiovascular safety was the open question for a decade, and the TRAVERSE trial answered a large part of it. In more than 5,000 men with hypogonadism and high cardiovascular risk, testosterone gel was noninferior to placebo for major adverse cardiac events over the follow-up window. The same trial recorded more atrial fibrillation, pulmonary embolism, and acute kidney injury in the treatment group. Both halves of that result belong in the consent conversation.
The routine risks are less dramatic and more common. Erythrocytosis is the most frequent adverse effect and the reason hematocrit is monitored on a schedule. Exogenous testosterone suppresses sperm production, which makes it functionally a contraceptive; a man who may want children needs that sentence said out loud before the first dose, not after. Prostate monitoring follows the guideline schedule, and the trial record to date has not shown an increase in prostate cancer over the windows studied, which is a statement about follow-up duration as much as about biology.
The clinical posture
Testosterone therapy, done to standard, is a diagnosis confirmed twice, a defined set of expected benefits, a monitoring calendar, and a stop rule if the benefits do not arrive. Done any other way, it is a subscription.
This article is education about a body of evidence. It is not a recommendation to start, stop, or dose any therapy, and individual decisions belong in a clinical conversation that includes the man’s full history, medications, and plans for children.