Testosterone starts to decline after the age of 30, but only by about by about 0.4% annually, explains Prof Wu; in men, there is no equivalent of the female menopause in which the ovaries stop functioning and oestrogen levels go into rapid freefall. In fact, adds Dr Richard Quinton, consultant endocrinologist at Newcastle University, the main reason some older men have low testosterone levels is not the so-called “manopause” but underlying problems such as obesity, and age-related illnesses such as type 2 diabetes and heart failure. Heavy drinking, stress, depression, and medication – including certain painkillers - can also lower T levels. “We men are hardwired to shut down testosterone levels when we are ill,” he explains. “In these cases it is the underlying problem which needs treatment, not the low testosterone levels.”