Anabolic Steroids Are Androgen Derivatives That Exert Negative Feedback on the Hypothalamic-Pituitary-TesticuIarAxis
The use of anabolic steroids has become widespread in human and animal athletes as many attempt to increase performance. Testimonials from veterinarians, physicians, human athletes, and trainers indicate that improvements in the athlete’s mental attitude, stamina, and physical strength are attained after anabolic steroids are administered.
The major concern is that many individuals receiving anabolic steroids are peripubes- cent or prepubescent. Anabolic steroids are androgen derivatives that have been altered to maximize their anabolic action and to minimize their androgenic side effects. It is not yet possible, however, to produce anabolic steroids that are devoid of androgenic activity, and many of the undesirable side effects of these drugs are caused by their androgenic activity. The adverse reproductive side effects observed with anabolic steroid use are similar to those associated with testosterone administration. Sustained testosterone or anabolic steroid administration affects pituitary function and leads to long- lasting impairment of testicular endocrine function. Potential side effects of the use of anabolic steroids in young animals may lead to incomplete development of the hypothalamic- pituitary-gonadal axis. The long-term side effects of anabolic steroid use on reproductive parameters in sexually immature animals are not yet known.A high percentage of colts and stallions in training or racing receive androgenic drugs, including anabolic steroids, and these horses have smaller testicles than similar horses not receiving such drugs. Only two anabolic steroids, Stanozolol and boldenone undecylenate, are approved by the U.S. Food and Drug Administration (FDA) for use in horses. Neither of these is approved for use in stallions. The administration of anabolic steroids to stallions has been shown to reduce seminal quality, daily sperm output, daily sperm production, and testicular size.
These effects most likely result from a negativefeedback mechanism on gonadotropin release from the pituitary. Alterations in seminal parameters are also observed, including depression of sperm concentration, sperm motility, and total number of sperm per ejaculate. Histological examination of the testes demonstrates a reduction in the number of developing germ cells other than type A spermatogonia. In addition, the mean diameter of Leydig cells is decreased, and changes indicative of testicular degeneration, including marked cytoplasmic vacuolization, shrunken tubules and Leydig cells, and phagocytosis of spermatids by multinucleated giant cells, have been observed. These adverse effects on the testes tend to be more severe in younger stallions. Repeated implantation of anabolic steroids in prepubertal bulls also results in decreased testicular size. Effects on testicular growth depend on the type of anabolic steroid administered, the age of the patient, and the dosage and duration of therapy.Human studies, which did not directly investigate the effects of anabolic steroids on spermatogenesis, also found reduced levels of circulating gonadotropins, testosterone, or both. Individuals using high doses of testosterone and anabolic steroids for only 3 months still had Iiypogonadotropic hypogonadism 3 weeks after the cessation of drug use. The presence of atrophic testicles and low LH, FSH, and testosterone levels after drug withdrawal indicates that long-term androgenic or anabolic steroid use affects pituitary function and leads to long-lasting impairment of testicular endocrine function.
Questions regarding the possibility of permanent sterility or testicular atrophy with long-term anabolic steroid use have not been answered for adults, and even less is known about the effects in prepubertal or peripubertal individuals. Indirect evidence suggests that prepubertal individuals may be at a higher risk for permanent derangements from anabolic steroid use than adults. 'Lherefore the use of anabolic steroids in males intended for breeding should be strongly discouraged.