Recently in the news, Clemens is being tried for having used human growth hormone to enhance performance. This hormone has been in the news around the world many times and in many countries. All athletes are screened for this substance and there is a general prohibition on its uses in all sports.

So what is human growth hormone anyway?

Well, it is basically exactly what it sounds like. In the body during puberty and slightly beyond (especially in males) the hormone is secreted to promote rapid growth. Muscle mass goes up, immunity and metabolism goes up - it is basically the magical substance that makes you a super-person. All animals have it, and for most animals it is secreted much earlier in life because they need to grow to survive on their own. Giraffes, for example, grow a foot a day when they are born.

In sports, human growth hormone is banned because of the obvious advantages it provides. In maintaining a "fair play" morale, this substance is illegal and can land an athlete behind bars or with serious fines and a ruined reputation.