Dimeric inhibin: a direct marker of ovarian aging.

OBJECTIVE: To investigate whether luteal secretion of inhibin-a is altered in the perimenopausal transition and to evaluate whether luteal inhibin secretion is correlated with other markers of ovarian reserve such as FSH and inhibin-b.
DESIGN: Prospective study.
SETTING: Reproductive Endocrinology Laboratories at The Ohio State University. PATIENT(S): Twenty-five women 39-52 years of age with regular menstrual cycles. INTERVENTION(S): Daily urine samples were monitored (LH predictor kit) to identify the day of ovulation. Blood samples obtained on days 6 and 8 after the LH surge and on day 3 of the subsequent follicular phase were assayed for FSH, E2, progesterone. inhibin-a, and inhibin-b. MAIN OUTCOME MEASURE(S): Serum levels of inhibin-a, inhibin-b, FSH, E2, and progesterone. RESULT(S): Luteal phase inhibin-a and follicular phase inhibin-b were correlated inversely with age in perimenopausal women. In addition, luteal phase inhibin-a and follicular phase inhibin-b levels were correlated inversely with follicular phase FSH levels. CONCLUSION(S): Both luteal phase inhibin-a and follicular phase inhibin-b levels are correlated inversely with age during the fifth decade of life. These findings suggest that corpus luteum function is altered during the perimenopausal transition. Moreover, these direct measures of ovarian function may be more sensitive indicators of "ovarian reserve" than indirect indicators such as pituitary FSH secretion.