Testosterone in men is an important sex hormone which regulates libido (sex drive), body mass, strength as well as being involved in the production of red blood cells and sperm.

As men get older, the amount of testosterone they produce falls. Some of the testosterone in men is converted to another hormone called oestrogen (specifically oestradiol). Oestradiol helps with libido and erectile function and so, as testosterone levels drop, so too does the level of oestradiol.

It’s not just age though that can reduce testosterone production. Overtraining and/or under fuelling in exercise can also result in low testosterone levels.