Aspects on the formation and detection of tissue levels of anabolic steroids in domestic animals

Abstract

Anabolic agents used in animal production can be classified according to their biological activity into compounds with oestrogenic, androgenic and gestagenic activity and according to the structure into endogeneous steroids, extraneous steroids and non-steroidal compounds. Metabolism of endogenous steroids is well established, a major principle being the formation of biologically less active metabolites, whilst the metabolism is not yet fully understood for non-endogenous steroids. Differences between compounds exist and it can be assumed that those with a high oral activity are only to a small extent biodegraded. Tissue residues of anabolic steroids can be expected in the ng/g to pg/g range. By using radioimmunoassay techniques, these low level residues and the naturally occurring tissue-concentration of endogenous steroids can be quantitated. Depending on the. animal and the tissue, endogenous steroids exhibit large variations. Oestrone was > 2 ng/g in muscle from a pregnant cow and, like oestradiol-17β, generally < 0.1 ng/g in all tissues in veal-calves, heifers and steers. Testosterone was highest in the bull (0.5 ng/g–11 ng/g), then the heifer (0.1 ng/g–0.6 ng/g) and veal-calf (0.02 ng/g–0.3 ng/g). Progesterone in fat was > 300 ng/g in pregnant cows and 17 and 6 ng/g in non-pregnant heifers and calves respectively. After implantation of 20 mg oestradiol-17β combined with 200 mg testosterone or progesterone into veal-calves 70–77 days before slaughter the oestrogen-tissue concentrations were <0.1 ng/g and the testosterone and progesterone concentrations were slightly elevated but still lower or in the same range as in heifers. Implantation of 140 mg trienbolone acetate (TBA) into veal-calves 70–77 days before slaughter yielded residues of free trienbolone between 0.13 and 0.5 ng/g. It is concluded that endogenous hormones are natural constitutents of edible animal tissue and that the amount of residues present in treated or untreated animal will not measurably contribute to the levels already seen in the human. In the case of extraneous compounds residues should be graded according to normal toxicological criteria.