Inhibin A and B as markers of menopause: a five-year prospective longitudinal study of hormonal changes during the menopausal transition

OBJECTIVES: A more direct and precise hormonal marker of the menopause has been required for some time. The aim of this study was to identify the most accurate marker of the menopause, based on analyses of inhibin A and B, FSH, LH and estradiol (E(2)), among 59 healthy women without hormonal treatment during the perimenopause and early postmenopause. METHODS: Fifty-nine women, aged 46-56 years (mean age 51.2 years), were examined annually for 5 years during the menopausal transition and had venous blood drawn simultaneously for later analyses of the above-mentioned hormones. RESULTS: Inhibin A showed a steady decline from at least 4 years before the final menstrual period (FMP) until 1 year before menopause, whereas inhibin B had a shorter lasting decline from year 3 to year 2 before menopause, concomitant with a rise in FSH and LH. CONCLUSION: The present study confirmed previous observations that inhibin A had a continuous decline starting before the decline of inhibin B, suggesting that an increasing part of the cycle was anovulatory. The fall in inhibin B and the increase in FSH constitute markers of ovarian aging. One year prior to menopause neither inhibin A nor inhibin B could be detected. The disappearance of these peptide hormones is an important predictor of the approaching menopause.