Ovary removal increases risk of Parkinson's disease
Findings underscore the protective action of oestrogen on brain cells.
Women who have had both their ovaries removed are at double the normal risk of developing Parkinson's disease, according to a study of medical records stretching back half a century. But experts stress that ovary removal - or ovariectomy - can in many cases save lives.
Women's ovaries produce significant amounts of the hormone oestrogen, which has been shown to protect certain types of nerve cell. "It acts on cells to make them less susceptible to toxins," says Kieran Breen, director of research at the Parkinson's Disease Society in London. He adds that this may happen because the hormone activates certain genes that produce protective proteins.
The nerve cells that oestrogen seems to help include those in the substantia nigra, an area deep in the brain that controls voluntary movements. Patients with Parkinson's disease show degeneration in this region, leading to the disease's characteristic shaking and unsteadiness, explains neurologist Walter Rocca of the Mayo Clinic College of Medicine in Rochester, Minnesota.
Mayo Clinic College of Medicine
In addition to searching through the historical data, Rocca and his team conducted thousands of medical checks over the past five years to follow-up patients among the 5,000 women in the dataset.
Dissecting the data
About half of the women in the study had undergone an ovariectomy. Of these, 1,202 had both ovaries surgically removed. Although many of these had to undergo the procedure to rid themselves of cancerous ovaries, some chose it purely on an elective basis.
Doctors sometimes suggest an elective ovariectomy for patients who must have an open-abdomen hysterectomy - removal of the uterus. The extra step is intended to eliminate the future risk of ovarian cancer.
But the new findings cast some doubt on whether this is the wisest choice for all patients. Of the 2,485 women who had one or both ovaries removed, 43 developed Parkinson's symptoms, 25 of whom developed the full-blown disease. In contrast, among the roughly 2,500 women who did not undergo ovariectomy, only 29 developed symptoms, with 18 cases of full Parkinson's.
Removing the second ovary put patients at greater risk, as 15 of the 1,202 women who had both ovaries removed later developed Parkinson's disease, as against ten in the 1,283 women who had just one ovary removed.
Past investigations into the relationship between oestrogen and Parkinson's disease have been carried out on animals. "This study is a complete, important step forward because it is based on women," Rocca says. He presented the results this week at the annual meeting of the American Academy of Neurology in Miami, Florida.
Even with these new results, medical experts emphasize that a woman diagnosed with ovarian cancer should undergo ovariectomy. "In that case, it would not be appropriate for someone to say 'Don't do it to me'," Breen stresses.
But when considering it as a preventative measure, Rocca's team advises women to examine their family medical history for either cancer or Parkinson's disease. "You have to weigh the two sides and decide," says Rocca. "It would be very dangerous if people look at the study and take it out of context."
Rocca hopes that the study will allow women to make better-informed choices about their medical options. "When a woman is discussing her decision for the future, we will have a more complete picture of the pros and cons," he says.