Anabolic steroids can be distinguished according to their chemical structure (C18, C19 or C21) and origin (endogenous or xenobiotic). Apart from their hormonal activity and depending on the compound applied or combination used, anabolic steroids stimulate growth, leading to gain in protein deposition based on an improved food conversion rate. Estrone (E1), estradiol (E2) and estriol (E3) are the main natural estrogens. Only 17^-estradiol is used in anabolic preparations. By esterification of the OH-groups (positions 3 and 17) of 17^-estradiol, compounds with more efficient activity are obtained. Main synthetic estrogens are 17a-ethynylestradiol and mestranol. Testosterone, etiocholanolone, androster-one and 5a-dihydrotestosterone are among the main natural androgens. Esters of 17b-testosterone have been found in anabolic preparations used in meat production. Nandrolone (19-nortestosterone), norethandrolone, trenbolone, 4-chlorotestosterone, fluoxymesterone, 17a-methyltestosterone, stanozolol, bolde-none (1-dehydrotestosterone), dianabol (17a-methylboldenone) are some examples of androgenic steroids discovered in the past in Europe for cattle production. Progesterone is the main natural progestagen; semi-synthetic derivatives, such as acetate or caproate esters of 17a-hydroxyprogesterone, have already been demonstrated to be used. The most popular synthetic progestagens are medroxyprogesterone acetate, megestrol acetate, melengestrol acetate and chlormadinone acetate.

Throughout the EC the use of xenobiotic anabolic agents is prohibited in food producing animals and no residues of these anabolics should be present in animal products imported into or produced within the EC (Directive 96/22/EC).

0 0

Post a comment