ABSTRACT
Testosterone is one of a number of naturally occurring androgens. It is a steroid hormone released primarily by the Leydig cells in the testes, and to a lesser extent by the adrenal cortex. It serves as the primary male sex hormone and plays a key role in the development of male reproductive tissues and the promotion of secondary sexual characteristics, such as the growth of body hair. The hormonal response to endurance exercise has been studied for many years, predominantly using either running or cycling as the mode of exercise. Unsurprisingly, moderate- to high-intensity endurance exercise leads to increases in hormones that typically respond to stressful situations, such as cortisol, growth hormone and the catecholamines. With regards to extreme endurance exercise, it is important to consider the role the environment plays, as thermal conditions can increase the physical exertion. Athletes, particularly ultra-endurance athletes, often find themselves competing in extreme environmental conditions such as hot or cold and dry climates.
