Pharmacological and endocrinological studies on anabolic agents

Abstract

When used in connection with animal production the term "anabolic agents" covers a wide range. Ther steroidal male and female sex hormones are included in this list, as are the nonsteroidal estrogens. For the clinician and for the endocrinologist, anabolics are only steroids chemically related to testosterone and 19-nortestosterone. Estrogens, though possessing anabolic properties, too, do not belong to this class. This paper will deal with anabolic agents in in the stricter sense of which mainly trenbolone acetate combined with hexestrol has been recommended for bull and heifer fattening. To consider possible consumer injury from ingestion of meat from anabolic agent treated animals, it is necessary to know the pharmacological properties of the agents, the doses producing certain effects or might produce, and the levels of residues in the meat. Trenbolone acetate will be compared with the following anabolic agents: methenolone acetate, methandrostenolone, nandrone, androstanazole, and 19-nortestosterone. The activity spectrum of trenbolone acetate is similar to that of 19-nortestosterone or those anabolics that are derived from 19-nortestosterone. The compound has about three times stronger androgenic effect than testosterone propionate. Its index of dissociation between anabolic/androgenic activity is 2--3. This index is 3--10 for the other anabolic agents. As regards the virilizing potency, trenbolone acetate is also on the top of the list. It seems that androgenicity and degree of virilization run paralle. The antigonadotropic activity (inhibition of ovulation and testicular growth) of trenbolone acetate exceeds that of testosterone propionate by the factor 3. The compound is not estrogenic and seemingly not or only weakly progestationally active. In principle, the androgenic activity (symptoms of virilization) as well as the antigonadotropic effect (disturbances of the menstrual cycle in women, inhibition of spermiogenesis in men) of trenbolone acetate might be noted. This risk, however, can be excluded by mere calculation. In rats, 0.1 mg/kg trenbolone acetate have an antigonadotropic effect. This corresponds to a daily dose of 5--7 mg in humans. By the same extrapolation, a daily human dose of 100 mg can be calculated for androgenic activity. Such factors of conversion are, of course, not precise because rats are much less sensitive to androgens and anabolics than humans. Thus, testosterone propionate is active only in daily doses of 10--20 mg. If in humans trenbolone acetate also has three times the activity of testosterone propionate, effects in man had to be counted with not less than a daily intake of 3--5 mg trenbolone acetate. The dose which is recommended for livestock fattening is 300 mg. IT can, therefore, be excluded almost with certainty that the meat would contain such large amounts of hormone residues.