Anabolic and androgenic steroids are available as prescription medications to be used in cases in which the body does not make enough hormone and supplementation may be required. Some hormone supplements in this pathway include growth hormone and testosterone itself. These medications are legally prescribed by health-care providers, but this group of drugs is often used illegally and abused to help increase athletic performance and improve body appearance. When used in a well-nourished body, anabolic steroids will cause weight gain primarily due to an increase in muscle mass.
All anabolic steroid use not prescribed by a licensed physician, is more properly defined as “ steroid abuse ”.ÂÂÂ The reason for this is simple, “ Steroids are very powerful hormones that can be extremely dangerous!”ÂÂÂ They can cause a variety of health problems some of which can have lasting ramifications.ÂÂÂ Although the twenty-three steroid related dangers listed below are not exhaustive, they certainly illustrate the risks and potentially harmful effects abusers face.
2) Irreversible adaptation to sperm competition . It has been suggested that the ancestor of the boreoeutherian mammals was a small mammal that required very large testes (perhaps rather like those of a hamster ) for sperm competition and thus had to place its testes outside the body.  This led to enzymes involved in spermatogenesis, spermatogenic DNA polymerase beta and recombinase activities evolving a unique temperature optimum, slightly less than core body temperature. When the boreoeutherian mammals then diversified into forms that were larger and/or did not require intense sperm competition they still produced enzymes that operated best at cooler temperatures and had to keep their testes outside the body. This position is made less parsimonious by the fact that the kangaroo , a non-boreoeutherian mammal, has external testicles. The ancestors of kangaroos might, separately from boreotherian mammals, have also been subject to heavy sperm competition and thus developed external testes, however, kangaroo external testes are suggestive of a possible adaptive function for external testes in large animals.