Pregnanediol excretion in fertile women: age-related changes.

In normal women reproductive capacity diminishes with age; the decline has been detected before the start of the menopausal transition. It is known that in premenopausal women most menstrual cycles are ovulatory. An investigation was set up to examine the possibility that there is an age-related decline in the ability of the corpus luteum to secrete progesterone at this time. Once-weekly urine samples for the measurement of pregnanediol were collected from 100 women aged 20-48 years, all of whom had regular 20- to 35-day menstrual cycles (1124 samples collected during the course of 312 menstrual cycles of which 96.8% were ovulatory). Pregnanediol excretion rates parallel the levels of progesterone in plasma. Examination of the rank correlation between age and pregnanediol excretion identified a significant negative correlation during the early and mid-follicular phases, but failed to detect any age-related change during the luteal phase. The evidence does not support the concept of an age-related increase in luteal phase defects before the start of the menopausal transition.