I Had an Ovary Removed. What Does That Mean for Perimenopause?

At age 42, I’ve just had one ovary removed because of a large cyst. What impact might I expect from having only one ovary in perimenopause?
—Kate

In medical school we were often told we had two of many organs so that if one stopped working or was removed, our body would still function normally. Generally this is true. If one kidney is removed, the other kidney picks up the slack without your even noticing. Same for adrenal glands and testes.

However, we know that women are born with all the eggs they will ever have, roughly equally divided between our two ovaries. We also know that menopause occurs when the last egg has been ovulated. So what happens when you cut the existing number of eggs in half by removing one ovary?

You aren’t the only one interested in answering this question. Two registry studies, one in Norway and one in Denmark, compared the average age of menopause in women with one ovary compared to women with two ovaries. Each of the two studies enrolled more than 20,000 women, about 1,000 of whom in each study had previously had one ovary removed.

In both studies, the women were surveyed regarding their menstrual cycle and their age at menopause. In both trials the average age of menopause was slightly earlier in the women who had one ovary compared to the women who had two ovaries — by 1 year in the Norwegian group and 1.8 years in the Danish group. These studies did not collect data on perimenopausal symptoms.

A German review of the literature did not find a difference in the age at menopause. The researchers did note that women who had one ovary removed had lower ovarian reserve, a diagnosis given when women undergoing fertility treatment have low levels of anti-Mullerian hormone and whose ovaries don’t respond as expected to the medications given to stimulate egg maturation. Low ovarian reserve does increase the risk of primary ovarian insufficiency — hormone levels consistent with menopause in women before age 40. Here again, women’s perimenopausal symptoms were not assessed.

None of these studies look at whether the woman’s age at the time the ovary is removed or the reason why the ovary was removed impacts future fertility or age at menopause. We don’t know if having an ovary removed in your teens or 20s has a greater impact than if you have an ovary removed in your 40s.

The takeaway: Having an ovary removed may be associated with slightly earlier menopause, but not by much. It is not clear that having one ovary has any impact on perimenopausal symptoms.