Postmenopause is associated with a decrease in serum inhibin A and inhibin B levels but not in activin A

Objective: The aim of the present study was to evaluate the changes in serum inhibin A, inhibin B and activin A levels in postmenopause. Methods: Specific assays for inhibin A, inhibin B and activin A were used and two groups of women were studied: 1) postmenopausal (n = 55) (aged 48-59 years), with a subgroup of 18 surgical menopause; 2) fertile healthy women (n = 50) (aged 19-35 years). The assays for inhibin A, inhibin B and activin A were two-site enzime immunoassay based on the use of plates coated with specific monoclonal antibodies; serum FSH, LH, 17β-estradiol levels were determined by radioimmunoassay. Results: Mean +/- SEM serum inhibin A and inhibin B levels in postmenopausal women were significantly lower than in fertile women (p < 0.01). The decreased levels of both inhibins were independent of the length or the type of menopause (natural or surgical). No significant difference of activin A levels was observed between postmenopausal and fertile women. Conclusion: The present study showed that both inhibin A and inhibin B levels decrease in postmenopausal women independently of age, length and form of menopause and they may represent a distinctive marker of ovarian failure. No changes of activin A levels has been observed after menopause suggesting that ovary is not the major source for circulating activin A.