CLASSIFICATION OF MENSTRUAL CYCLES IN PRE- AND PERIMENOPAUSAL WOMEN

Urine for the analysis of pregnanediol, oestrogens, FSH and LH, was collected weekly from 50 normal menstruant women. Twenty of these women were aged ≥ 40 years and had a history of regular menstrual cycles; they are termed premenopausal. The other 30 reported a recent break in regular cyclicity and are termed perimenopausal. All menstrual cycles observed in the premenopausal women were ovulatory in type and 25–30 days in length. The 124 cycles observed in the perimenopausal women were 18–260 days in length (median, 29 days), with 52% of the ovulatory type. To describe this diversity, a systematic classification is proposed based on (1) the excretion of pregnanediol in the 12 days preceding menstruation (classes I–IV), (2) gonadotrophin output (categories A–E, and L), and (3) the length of the menstrual cycle in days. The premenstrual surge of pregnanediol was greatest in class I cycles and diminished progressively until it became undetectable in class IV. Gonadotrophin excretion was lowest in category A cycles and increased progressively until all levels were within the postmenopausal range by category E. In cycles of category L only LH (and not FSH) was raised. In the perimenopausal women 37 cycles included episodes of high gonadotrophin excretion (categories C–L), a phenomenon which was not seen in the premenopausal women. These cycles were usually longer than 50 days and were often anovulatory in type (classes II—IV). Typically they began with the high gonadotrophin levels and the low oestrogens which characterize the postmenopausal state, and ended after a rise in oestrogen output to levels ≥ 70 nmol/24 h. It is concluded that 'anovulatory' cycles and cycles in which there are 'postmenopausal' levels of FSH and LH are common in the perimenopause and that they are rare in premenopausal women.