Effects of androgen (testosterone, 5 alpha-dihydrotestosterone, 19-nortestosterone) administration on growth in...

The present studies examined the effect of three androgens, testosterone, a reduced form 5 alpha-dihydrotestosterone (5 alpha-DHT), and the readily aromatizable anabolic androgen, 19-nortestosterone, on growth in male and female turkeys. Growth (body weight, average daily gain, and right breast muscle weight) was increased by testosterone (females), 5 alpha-DHT (males and females), and 19-nortestosterone (males and females). Moreover, both feed:gain ratio and the weight of abdominal adipose tissue was reduced in turkeys treated with testosterone (females), 5 alpha-DHT (males and females), and 19-nortestosterone (females and males). Bursa of Fabricius weights were reduced in androgen-treated male or female turkeys with the decrease following 19-nortestosterone being greater than those observed with either testosterone or 5 alpha-DHT. Androgen treatment had no effect on skeletal growth (as indicated by shank-toe length) or weights of the liver, spleen, or testes. In female turkeys, plasma concentrations of hormones were determined following androgen treatment. No effects were observed on plasma concentrations of insulin-like growth factor-I or luteinizing hormone after any androgen treatment. Testosterone administration was followed by a physiological increase in the plasma concentrations of testosterone. Plasma concentrations of growth hormone were unaffected by either 5 alpha-DHT or 19-nortestosterone but reduced by the high dose of testosterone. The effect of castration on growth in the presence or absence of 19-nortestosterone was also examined. Castration did not depress growth compared with sham-operated controls, but increased adiposity. 19-Nortestosterone increased growth of castrated turkeys, increased muscle weight, and reduced abdominal adipose tissue weight.