Technische Universität München

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Anabolic agents are chemical compounds capable of enhancing the anabolic processes in the organism. They affect protein metabolism by stimulating protein synthesis (anabolic effect) and inhibiting protein breakdown (anticatabolic effect).
The anabolic active substances included in the 2008 Prohibited List are subdivided into the group of anabolic androgenic steroids and the group of other anabolic agents.  

Anabolic androgenic steroids (AAS)
The group of anabolic androgenic steroids (AAS) includes the endogenously produced testosterone, dihydrotestosterone (DHT), testosterone prohormones and their metabolites as well as exogenous anabolic androgenic steroids, which are synthetic derivatives of testosterone.
Testosterone, the primary male sex hormone, is both an anabolic and androgenic steroid. It is synthesized from cholesterol in the Leydig cells of the testes. Small amounts of testosterone are also secreted from the ovary and the adrenal gland. DHT is an active metabolite of testosterone and a potent androgen in some tissues. Dehydroepiandrosterone (DHEA), androstenedione and androstenediol are steroids in the sex hormone biosynthesis pathway and are precursors in the endogenous production of testosterone and estrogens. These steroid precursors are weak androgens secreted primarily by the adrenal glands in both sexes. They provide a pool of circulating steroids that can be converted to active androgens and estrogens in the peripheral tissues.
Testosterone exerts no significant effect on the human body if administered orally or parenteral because the hormone is rapidly metabolized by the liver; it must be modified chemically to produce clinically useful preparations. In addition, the therapeutic index of testosterone is 1 which means that there is similarity in the proportion between anabolic and androgenic effects. Synthetic AAS are, therefore, developed to retard the hormone’s degradation process and also to dissociate its androgenic and anabolic effects so that only the anabolic effects can be sustained while the androgenic side effects are reduced to a minimum. The major modifications of the testosterone molecule are alkylation at the 17α-position (orally active compounds) and esterification at the 17β-position (parenterally active compounds).

Other anabolic agents
The group of other anabolic agents includes various exogenous substances with anabolic side effects - clenbuterol, zilpaterol, zeranol, tibolone. Clenbuterol is an effective bronchodilator drug used in the treatment of asthma. Zeranol is a mycoestrogen with non-steroidal structure synthesized by molds (fusarium species) commonly contaminating grain. Tibolone is a synthetic steroid with mixed properties of estrogen, progesterone, and androgen. Selective androgen receptor modulators (SARMs) are new non-steroidal substances in preclinical development.