Decreased inhibin tone and increased activin A secretion characterize reproductive aging in women

Objective: We hypothesized that the increased FSH noted in older reproductive-aged women is due to both decreased inhibin and increased activin A secretion. Design: Comparative clinical study. Setting: An academic research center. Patient(s): Five cycling women, aged 43 to 47, were compared to five midreproductive women. aged 19 to 38, Intervention(s): Specimens taken every 2 to 3 days were assayed for inhibin A and B and activin A. Main Outcome Measure(s): Integrated concentrations of inhibin A: inhibin B, and activin A in the follicular phase, luteal phase, and whole cycle. Result(s): Follicular inhibin B was reduced in older versus younger women (504 +/- 82 versus 748 +/- 72 total pg). Luteal inhibin A was reduced in older versus younger women (668 72 versus 1152 +/- 216 total pg). Activin A was elevated throughout the cycle of older versus younger women, without within-cycle fluctuations (21 +/- 2 versus 11 +/- 1 total ng). Conclusion(s): Lack of restraint by inhibin A and inhibin B contributes to the FSH rise associated with reproductive aging. This loss of restraint occurs in a tandem fashion, with inhibin B reduction before ovulation and inhibin A reduction after ovulation. Activin A may FSH in older reproductive-aged women. (Fertil Steril(R) Reproductive Medicine.) also play an endocrine role in maintaining elevated 1999,71:658-62. (C)1999 by American Society for Reproductive Medicine.).