Estrogen loss during childbearing years may increase a woman's risk for Parkinson's disease.

Mayo Clinic researchers report that women who have had their ovaries surgically removed are at increased risk for developing Parkinson's disease later in life.

"The risk is higher — about double — for women with both ovaries removed. However, even removing one ovary may increase the risk of Parkinson's disease," says researcher Walter Rocca, MD, professor of neurology and epidemiology.

The younger a woman is at the time of the surgery, the higher her risk of the neurological disorder, he tells WebMD. Parkinson's disease is marked by tremors, rigidity, and trouble with balance and coordination.

The study involved nearly 2,500 women. Half of them previously had one ovary removed, while the others had both removed. For comparison, the researchers also evaluated the risk of Parkinson's disease in a group of 2,387 women of the same age who had not undergone ovarian surgery.

The study was presented today at the annual meeting of the American Academy of Neurology.

The increased risk of Parkinson's disease is not due to the surgery itself, Rocca says, but the subsequent drop in estrogen levels.

"There is biological evidence from animal studies that estrogen is protective for the specific part of the brain that is involved in controlling movements," he says. "Damage to this part results in Parkinson's disease."

The Estrogen Connection

Removal of the ovaries is the major cause of reduced estrogen.

"The new study is the first to directly link ovary removal and Parkinson's disease," he says. "And ovary removal is the most direct surrogate for low estrogen stores."

Women who underwent removal of both ovaries had twice the risk of Parkinson's disease compared with women who did not undergo surgery. Women with one ovary removed experienced a 40% increased risk of developing Parkinson's disease.

Rocca's previous study suggests that the younger a woman's age during the natural menopausal transition, the higher the risk of Parkinson's disease.

Stanley Fahn, MD, professor of neurology at Columbia University in New York and past president of the American Academy of Neurology, says the estrogen connection is intriguing.

"The study fits with indirect evidence that estrogen might be protective against Parkinson's disease," he tells WebMD.

Weighing the Risks and Benefits of Ovary Removal

Many women who are having one ovary removed because of cancer or a benign cyst decide to have the other ovary removed as a preventive measure at the same time, Rocca says. Likewise, some women undergoing a hysterectomy — the surgical removal of the uterus — also opt to have one or two ovaries removed.

He advises women who are thinking about preventive removal of the ovaries to weigh the new findings when making their decision.

"Our data suggest that this is not a good idea, at least in terms of your brain," Rocca says. "Pros [of ovary removal] include cancer prevention, but cons are your bone and brain health. The decision has to be made on a case-by-case basis."

For those women having cancer-ridden ovaries removed, the decision is unambiguous, he adds. "If you have cancer in the ovary, you want to cut it out."

By Charlene Laino, reviewed by Brunilda Nazario, MD

SOURCES: American Academy of Neurology 57th Annual Meeting, Miami Beach, Fla., April 9-16, 2005. Walter Rocca, MD, professor of neurology and epidemiology, Mayo Clinic, Rochester, Minn.