Does testosterone decline in men with age, and should you do something about it?

Yes, testosterone really does decline with age, and this is solidly established. The decline begins on average around age 35 to 40 and amounts to roughly 1 to 3 percent per year. Above the age of 60, about one in five men has formally low levels; above 80, that applies to half of all men. Notably, in American men a separate, population-wide decline has also been found that is larger than what ageing alone can explain. Obesity or smoking cannot fully account for this.

Lower testosterone is associated in observational studies with greater muscle loss, more fat accumulation, a worse cardiovascular profile and possibly a higher risk of dementia. But the direction of causality is not always clear: poorer general health can also suppress testosterone, rather than the other way around. Low testosterone is, for many of these outcomes, a signal, not a proven cause.

Testosterone therapy (TRT) has the strongest evidence for sexual function and quality of life in men with established hypogonadism (a medically confirmed testosterone deficiency). In a randomised trial in 788 men aged 65 and older, sexual function improved significantly after one year of TRT¹. Another study in more than a thousand men aged 50 to 74 suggested that TRT may reduce the risk of type 2 diabetes in men with a large waist circumference and low testosterone². The latter is promising, but still requires confirmation.

For cognition and physical performance the picture is different. Observational studies link low testosterone to cognitive decline, but randomised trials show no improvement in memory or cognitive function after TRT. For muscle function and mobility, the effects are limited or absent. The idea that TRT halts muscle loss or memory decline is not clinically proven.

Do you have symptoms and are you considering taking action? Be aware that a low result does not automatically mean ordinary ageing. It may also point to a condition of the pituitary gland or the control centre in the brain that regulates hormones. Medical investigation is necessary before starting therapy. Strength training produces a temporary rise in testosterone, but whether this delivers structural health benefits through testosterone has not been demonstrated.