Peripheral plasma oestradiol-17β and progesterone levels in female goats induced to hypothyroidism

Abstract

Subcutaneous injections of thiourea were given to five mature female goats, initially at the rate of 100 mg kg −1 body weight per day for 15 days and then at 66.7 mg kg −1 body weight per day for the following 15 days. Triiodothyronine (T3) and thyroxine (T4) plasma levels were reduced during the period of thiourea treatment. This confirmed successful induction of hypothyroidism. Behavioural oestrus was exhibited by three animals on day 22, and by two animals on day 23 of thiourea treatment, whereas in the control group oestrus was observed on days 19–20. The symptoms of behavioural oestrus in treated females were partially suppressed; however, the duration of oestrus was 48–50 h compared with 36–48 h in control animals. Plasma oestradiol-17β and progesterone levels during the oestrous cycle in thiourea-treated goats were lower ( P < 0.05) than in control animals and when artificially inseminated, treated goats did not conceive. The results of this experiment confirm the hypothesis that the thyroid is involved in maintenance of the reproductive process.