Bioscientifica Proceedings

Summary. It is proposed that the first follicular phase in the lamb is initiated when responsiveness to oestradiol inhibition of LH secretion decreases sufficiently to permit the expression of an inherent hourly LH pulse rhythm. The hourly LH pulse rhythm is believed to drive oestradiol production to levels that induce the first LH surge. This hypothesis is based upon several considerations. First, pulsatile LH secretion invariably occurs at low frequencies in...