For all its reputation, testosterone plays a much bigger role in the body than one might think.

A type of sex hormone, testosterone indeed helps regulate libido and sexual function in men (and women, it should be added). But it’s also responsible for maintaining muscle mass, bone density and fat distribution, and it can even affect your mental wellbeing.

Lots of things can affect testosterone levels, including lifestyle factors like diet, sleep, stress and weight. Age can too, as the glands responsible for regulating testosterone decline over time, along with certain medical conditions like diabetes and genetic disorders.

Whatever the cause, low levels of testosterone can not only result in a decline in sex drive and function, but can also contribute to a range of symptoms, including decreased muscle mass, weight gain, mood changes, fatigue and even osteoporosis (weakening of bone).