Testosterone is responsible for libido and also "stamina" during sex. In addition, it promotes protein synthesis which, in turn, promotes muscle growth. Testosterone also works at breaking down the fat on the stomach and hips. Testosterone also has a number of psychological effects: strength, assertiveness and energy. It facilitates signal transmission in the brain and thus promotes stereoscopic vision, for instance, while having an overall positive effect on thought processes, coordination and memory.

All men are able to stimulate the production of testosterone in their bodies themselves. Important in this respect is regular endurance and weight training. The body produces what it needs: by training the muscles, the body produces hormones with stimulate muscular development. The regular consumption of alcohol in large quantities, on the other hand, will cause a long-term reduction in testosterone levels. As a guideline: no more than 0.2 l wine per day. What is quite clear is that sex has a major influence on the production of testosterone. Regular sex keeps testosterone production in full swing.

Oestrogens are also found in men, if only at 1/10 of the level that is found in the female body. They help to stabilise the bones and protect against osteoporosis. Oestrogens also protect the blood vessels and can therefore prevent heart attacks.

If a man is overweight, has a fatty liver, (the onset of) diabetes or enlarged breasts, it is important to check his oestrogen levels.

DHEA (dehydroepiandrosterone) is known as a hormone precursor: it can be converted into testosterone, but also oestrogen, depending on what is needed by the body. In the same way as testosterone, it improves memory performance, builds up muscles and to a certain degree burns fat. DHEA is often described as a "youth hormone". Studies have demonstrated that if DHEA levels are reduced, substitution for such a deficiency enhances wellbeing and can also increase physical fitness.

Concentrations of DHEA decrease continually after the age of 30. A loss of libido, impaired concentration and frequent infections may be indications of low DHEA levels.

The human growth hormone (HGH) works the same in many ways as testosterone and DHEA. It stimulates muscle growth and burns fat. It is widely used as a doping agent for enhancing performance. On top of this, HGH helps to keep skin firm by stimulating collagen synthesis. HGH also has a positive effect on our moods. As with DHEA, the production of HGH decreases with age. The injection of this growth hormone for the purposes of anti-aging treatments is highly controversial and in the majority of cases is not advisable.

The development of sperm in the testicles depends on the regulated production of hormones in a man's body. As in women, the hormones LH and FSH, which are produced in the pituitary gland, play a pivotal role. The follicle-stimulating hormone FSH causes the sperm to mature in the seminiferous tubules; the luteinising hormone LH effects the production of testosterone, but also influences sperm maturation. The time taken for spermatazoa to fully mature and leave the testicles is 3 months, at which point the now viable sperm enter the epididymis, where they remain until ejaculation. It is interesting to also mention that a healthy man can produce up to 100 million sperm every day.