INFLUENCE OF ANDROGENS ON PLASMA-CONCENTRATIONS OF GROWTH-HORMONE IN GROWING CASTRATED AND INTACT CHICKENS

Castrated chicks implanted with testosterone or 5α-dihydrotestosterone (5α-DHT) had circulating concentrations of the respective androgen similar to or less than in shamoperated chicks. In castrated chicks, 5α-DHT or 19-nortestosterone (19-NorT) inhibited growth as indicated by body weight, while testosterone and 5β-dihydrotestosterone (5β-DHT) were without effect. In intact male or female chicks, growth was inhibited by either testosterone or 5α-DHT but was unaffected by 5β-DHT or estradiol-17β. Plasma concentrations of luteinizing hormone (LH) were reduced in castrated chicks receiving implants of either testosterone or 19-NorT. Only the highest dose of 5α-DHT depressed the circulating concentration of LH; lower doses of 5α-DHT being without effect. During the first 6 weeks of growth, plasma concentrations of GH were unaffected by most steroid treatments (5α-DHT, 5β-DHT, low doses of testosterone, estradiol-17β) in castrated or in intact male or in female chicks. Similarly, 19-NorT did not affect plasma concentrations of GH in castrated chicks. The high dose of testosterone, however, depressed plasma concentrations of GH in castrated chicks between 2 and 6 weeks of age. Between 8 and 12 weeks of age, all steroids tested, except 5α-DHT, were without effect on plasma concentrations of GH. Plasma concentrations of GH were increased in 5α-DHT-treated chickens. This effect was observed irrespective of dose of 5α-DHT or whether the androgen was administered to castrated or to intact male or to female chicks. © 1990.