Adrenal function in lambs treated with androgenic and oestrogenic growth stimulants

Abstract

Three experiments were carried out in which plasma cortisol concentrations were measured hourly in lambs treated with various anabolic steroids. In the first experiment, female lambs were implanted with trenbolone acetate (TBA) and plasma cortisol was measured for 24-h periods 4 weeks after implantation and 1 week after reimplantation. Plasma cortisol levels were unaltered 4 weeks after treatment, but were found to be significantly lower 1 week after retreatment. On this occasion, peak concentrations of cortisol after ACTH challenge were also reduced by TBA. In the second experiment, female lambs were implanted with a mixture of TBA and oestradiol and plasma cortisol measured 1 and 4 weeks later. Results were similar to the first experiment although the reduction in plasma cortisol was less. In the third experiment, castrated male lambs were implanted with either TBA, TBA plus oestradiol or a long-acting oestradiol implant. In this experiment, only oestradiol affected plasma cortisol levels, causing a large elevation. All three treatments stimulated growth. Measurement of bound and free cortisol concentration in the third experiment indicated that oestradiol treatment tended to increase the proportion of cortisol present in the free form.These results suggest that an inhibition of cortisol secretion may be important in the anabolic response of female sheep to TBA. In the male, however, cortisol concentrations are naturally lower and are not further reduced by TBA treatment.Plasma insulin concentrations were also measured in the castrated males. Neither TBA nor the combined implant altered insulin levels, but oestrogen treatment resulted in a small increase in insulin. The diurnal pattern of plasma insulin closely paralleled that of cortisol.

Growth performance and body composition of mature female sheep implanted with trenbolone acetate

“…These authors in common with others (e.g. Sillence, Thomas, Anil, Redfern and Rodway (1987) using 40 mg implants) did not measure overall effects on body composition.…”

Effect of anabolic implants on adrenal cortisol synthesis in feedlot beef cattle implanted early or late in the finishing phase

“…Previous work examining the effects of TBA and E 2 in female lambs suggests that the effects of implantation on cortisol concentrations may be a relatively short-term event. Sillence, Thomas [7], reported that plasma cortisol levels were lower but not significantly different in treated animals compared to non-implanted animals 4 wk after implantation. However, 1 wk after re-implantation with an androgenic and estrogenic growth stimulant, the implanted lambs had significantly lower plasma cortisol [7].…”

“…Sillence, Thomas [7], reported that plasma cortisol levels were lower but not significantly different in treated animals compared to non-implanted animals 4 wk after implantation. However, 1 wk after re-implantation with an androgenic and estrogenic growth stimulant, the implanted lambs had significantly lower plasma cortisol [7]. This is also consistent with loss of 21-and 11β-hydroxylase activity by androstenedione which occurred after only 1 h of exposure [18].…”

“…A similar reduction in plasma cortisol is observed in lambs administrated TBA or TBA plus E 2 [7]. Moreover, TBA implanted sheep have an impaired ability to respond to an ACTH challenge [7,8] further indicating that TBA decreases responsiveness of the adrenal gland glucocorticoid production.…”

“…Likewise, cortisol synthesis in non-stimulated and adrenocorticotrophic hormone (ACTH)-stimulated bovine adrenocortical cells is suppressed in the presence of testosterone, dihydrotestosterone and TBA [6]. A similar reduction in plasma cortisol is observed in lambs administrated TBA or TBA plus E 2 [7]. Moreover, TBA implanted sheep have an impaired ability to respond to an ACTH challenge [7,8] further indicating that TBA decreases responsiveness of the adrenal gland glucocorticoid production.…”