Release of LH during treatment with purified sheep FSH without signs of adequate follicular maturation in women.

Four amenorrhoeic women were treated with a purified sheep fsh preparation. During treatment, plasma progesterone, oestradiol and lh concentrations were measured every 24 or 48 hr. In all the women, an lh peak was found during treatment, even though in three of these there was no evidence of adequate follicular maturation, as assessed by plasma oestradiol levels. These results indicate that a peak of plasma oestradiol need not necessarily be the unique stimulus for lh release and the possibility that fsh in humans can stimulate lh release directly through a short loop feedback mechanism should not be disregarded. Recent studies on plasma oestradiol and lh levels have supported the growing view that a rise in the circulating oestrogen levels may provide the stimulus for pituitary lh release and subsequent ovulation (Catt, 1969; Corker, Naftolin &Exley, 1969). Further evidence that plasma oestradiol is the physiological trigger for the mid-cycle peak of lh has been provided by Vande Wiele, Bogumil, Dyrenfurth, Ferin, Jewelewicz, Warren, Rizkallah & Mikhail