COLUMBUS, Ohio -- New research suggests that measuring the levels of two specific ovarian hormones may help doctors better determine the reproductive potential of older women.
Researchers found that measuring the levels of the hormones inhibin-a and inhibin-b were a more sensitive test of a womans ovarian reserve -- or reproductive potential -- than the most commonly used test today. The current test measures the levels of follicle stimulating hormone (FSH).
Measuring inhibin levels may be a more accurate way to assess a womans fertility, said Douglas Danforth, associate professor of obstetrics and gynecology at Ohio State University.
Production of inhibin-a and inhibin-b drops as a woman goes through perimenopause, the phase just before menopause. Because the inhibins are produced in the ovaries, they can serve as a direct measure of ovarian function.
The research appears in a recent issue of the journal Fertility and Sterility.
Danforth and his colleagues measured hormone levels in 25 women aged 39 to 52. Women in this age range are usually considered perimenopausal. All subjects still had normal menstrual cycles. Blood serum samples were analyzed for the hormone levels during specific times of the menstrual cycle.
The results showed that levels of inhibin-a and inhibin-b were lower in the women aged 46-52 than in the women aged 39-45. This is consistent with the fact that older women, who are nearer menopause, should have reduced ovarian function compared to younger women, Danforth said. However, the results showed no difference between the older and younger women in terms of FSH levels.
This suggests that inhibin levels may be a more sensitive gauge of ovarian function than FSH levels, Danforth said. FSH levels alone may be a less reliable indicator of reproductive potential in older women.
While researchers had speculated that inhibin levels may be directly associated with ovarian function, until recently there had not been specific and sensitive tests for inhibin, Danforth said.
Testing levels of inhibin-a, inhibin-b and FSH in older women may provide the best method to determine the viability of an aging ovary, Danforth said.
Eggs develop within the sac-like follicles contained in the ovary. Secreted by the pituitary, FSH attaches to the surface of cells in these ovarian follicles. Inhibins participate in controlling FSH levels, Danforth said.
The decline in ovarian inhibins but not in pituitary FSH suggests that the inhibins may be a better and more direct marker of ovarian age than FSH, Danforth said.
Co-authors for this research included Laura Arbogast, Jamil Mroueh, Moon Kim, Elizabeth Kennard, David Seifer and Chad Friedman, all of the department of obstetrics and gynecology at Ohio State.