Serum inhibins, estradiol, progesterone and FSH in surgical menopause: a demonstration of ovarian pituitary feedback loop in women.

BACKGROUND The objective of this study was to confirm the source and study the acute changes and relationship between inhibins and FSH at surgical menopause. METHODS Regularly cycling women (42-47 years; n = 10) undergoing bilateral oophorectomy for non-ovarian pathology were recruited for this study. One blood sample was taken before surgery and after removal of the ovaries, samples were taken every 15 min up to 1 h, hourly up to 6 h, after 12 h and daily during the hospital admission (3 days). RESULTS There were five women in the follicular phase and five women in the luteal phase of the cycle. For women in both phases, levels of inhibin A, inhibin B, estradiol (E(2)) and progesterone decreased after the removal of the ovaries. Serum FSH levels started to rise after 12 h in both follicular and luteal phase women after the surgical menopause. Correlation analysis showed that inhibin A and E(2) were significantly negatively correlated in both phases with FSH concentration. Inhibin B had a negative correlation in the follicular phase and progesterone had a negative correlation in the luteal phase. CONCLUSIONS This study showed that ovarian inhibin A and B were cleared from the circulation within 12 h of oophorectomy, whereas E(2) and progesterone remain in the circulation for longer. Negative correlation between FSH, inhibin A and inhibin B suggests that inhibins may contribute to the observed early rise in FSH after the surgical menopause.