For how we live.
An analysis of 50 top-selling 'T booster' products found only 24.8% contained an ingredient with data showing it raises testosterone — and 10.1% contained something shown to lower it. Two herbs are partial exceptions.
Obesity and metabolic syndrome push men's testosterone down. One large trial shows testosterone can cut new diabetes modestly, but the effect is smaller than weight loss and comes with safety trade-offs.
The TRAVERSE trial cleared its cardiovascular safety in 5,246 high-risk men; the Testosterone Trials found a real but moderate sexual-function benefit. Guidelines reserve it for genuine, twice-confirmed deficiency.
A fear that shaped urology for decades held that raising testosterone feeds prostate cancer. Randomised trials and a large 2024 safety analysis find no such rise in screened men.
It anchors every male-infertility evaluation, but its reference numbers come from a few thousand fertile men — and a normal result never rules fertility in or out.
A meta-analysis of 11 trials put the change in a healthy man's resting testosterone from training at zero. Endurance work can lower it; losing body fat is the lever that reliably raises it.
One week of five-hour nights cut young men's daytime testosterone by 10–15% in a controlled study. Yet CPAP for sleep apnoea leaves the hormone unmoved, pointing back at body weight.
Testosterone raises desire mostly in men whose levels are genuinely low, and the effect is modest. In the largest trial, the size of the hormone rise, not a threshold, tracked with benefit.
Low testosterone is a symptom, not a diagnosis. It splits into testicular and pituitary causes — and Klinefelter syndrome, the commonest genetic cause, is found in only about a quarter of the men who have it.
Exogenous testosterone switches off the body's own signals to the testes. In a male-contraceptive trial, 95.9 per 100 men fell to near-zero sperm counts. The effect is usually, but not always, reversible.
Young men are chasing higher testosterone with 'natural boosters' and direct-to-consumer TRT. The supplements are largely unproven; unnecessary therapy carries real costs to fertility.
Researchers searched in four languages across three engines. One in ten clinics said it would prescribe testosterone to men with normal levels; one in five claimed it cuts cardiovascular risk.
The randomised evidence in older men found a moderate effect on sexual function and none on vitality or walking. A 5,246-man safety trial cleared it on heart attacks and found more fractures.
Two datasets report an age-independent fall in men's testosterone across birth cohorts. A separate study of nine thousand men found much of the variation between cohorts came from the tests themselves.