Old wisdom doesn’t always stand test of time

When I was a resident in training, there were certain rules we followed, rules passed down to us by our mentors, rules we didn’t question. One of those rules had to do with removing a woman’s ovaries at the time of hysterectomy. Back in those days (the late ‘70s and early ‘80s), the rule was if a woman was over 35 and scheduled for a hysterectomy, the ovaries should go too.

The rationale was this: Once childbearing is over, the ovaries aren’t necessary (!), and leaving the ovaries in leaves the risk of developing ovarian cancer, a particularly dastardly cancer and one that is difficult to diagnose early.

Well, as I got closer to 35, I figured that was a stupid rule, but most of us gynecologists recommended removing the ovaries at the time of hysterectomy if our patient was over 40, and if she was post-menopausal, we really pushed it. This tactic was supported by numerous studies, of varying quality.

I’m not talking about women who are high risk for ovarian cancer – those who have ovarian cancer scattered all over their family tree or who are carriers of the BRCA1 or BRCA2 gene. Since those women have a greater than 50 percent chance of developing ovarian cancer, they really should consider having their ovaries removed after childbearing is complete.

But what about women who are at average risk, who are having a hysterectomy for a noncancer related reason? Should we still be yanking those ovaries?

An article in this month’s journal Obstetrics and Gynecology attempts to answer this question. The authors tackled the question by doing a statistical analysis of risk. Rather than taking a large group of women and following them over time (a prospective study) or looking at a bunch of charts of women who’ve had hysterectomies (a retrospective study), they used published age-specific data for the risk of developing ovarian cancer, coronary heart disease, hip fracture, breast cancer and stroke in women who’ve had their ovaries removed at the time of hysterectomy and those who haven’t.

Then, they did a complicated statistical analysis that I can’t even begin to understand, much less explain. They looked at how many women would still be alive at age 80 based on whether they still had their ovaries.

The authors’ statistical model showed that women younger than 65 clearly benefited from keeping their ovaries in place at the time of hysterectomy. More of them would be alive at age 80, according to the model. For women younger than age 65 at the time of ovary removal, their risk of dying from coronary heart disease increased. For women older than 65, increased mortality came from hip fracture.

In this model, there was no survival advantage of ovarian removal at any age.

Several studies have shown that hysterectomy itself actually reduces the risk of ovarian cancer, even if the ovaries are left in place. Why that is, no one knows.

According to the Nurses’ Health Study, a well-run prospective study, taking out the ovaries increases a woman’s risk of cardiovascular disease, in some cases even doubling the risk.

Even after menopause, the ovaries continue to produce a small amount of a weak estrogen, as well as testosterone and a hormone with weak testosteronelike activity, androstenedione. Testosterone and androstenedione are partially converted to estrogen in a woman’s body, and all of these hormones may play a role in keeping bones strong.

This study has several weaknesses. First, it’s a statistical model, not a study of real live women. And the model is based on many other studies, of varying quality.

Still, while we wait for a confirmatory study, it should make all us gynecologists pause and consider whether the old wisdom is good wisdom. For women facing a hysterectomy for conditions other than cancer, it’s worth a good long talk with your doctor about whether the ovaries should go or stay.