Pituitary-ovarian relationships in women approaching the menopause.

With a view to evaluating pituitary-ovarian relationships in women approaching the menopause, serial determinations of basal body temperature (BBT) and of serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and oestradiol were performed in 5 pre-menopausal and 9 young women throughout a complete menstrual cycle. The hormone levels in the early follicular phase and on LH peak-days in the two groups were then compared. In the pre-menopausal group the age range was 43-45 yr and the length of the menstrual cycles investigated varied from 30-56 days, the BBT curves being biphasic. Two pre-menopausal women demonstrated concentrations of FSH and LH that were higher than those in the young women, even though their serum oestradiol levels in the early follicular phase remained within the upper and lower mean values observed in the young women. This finding confirmed that, in addition to reduced ovarian oestrogen secretion, another, as yet unknown, factor must exist, which can produce a rise in serum gonadotrophin levels in women approaching the menopause.