PERIPHERAL PLASMA ESTRADIOL-17-BETA AND PROGESTERONE LEVELS IN FEMALEGOATS INDUCED TO HYPOTHYROIDISM

Subcutaneous injections of thiourea were given to five mature female g oats, initially at the rate of 100 mg kg(-1) body weight per day for 1 5 days and then at 66.7 mg kg(-1) body weight per day for the followin g 15 days. Triiodothyronine (T3) and thyroxine (T4) plasma levels were reduced during the period of thiourea treatment. This confirmed succe ssful induction of hypothyroidism. Behavioural oestrus was exhibited b y three animals on day 22, and by two animals on day 23 of thiourea tr eatment, whereas in the control group oestrus was observed on days 19- 20. The symptoms of behavioural oestrus in treated females were partia lly suppressed; however, the duration of oestrus was 48-50 h compared with 36-48 h in control animals. Plasma oestradiol-17 beta and progest erone levels during the oestrous cycle in thiourea-treated goats were lower (P < 0.05) than in control animals and when artificially insemin ated, treated goats did not conceive. The results of this experiment c onfirm the hypothesis that the thyroid is involved in maintenance of t he reproductive process.