NEW YORK, NY -- Oct. 13, 1998 -- New research suggests hormone replacement therapy may help prevent the onset of Parkinson's disease, as well as alleviate some of the symptoms of the devastating disorder.

The preliminary findings of four studies on the estrogen/Parkinson's disease connection were presented here today at the fifth International Congress of Parkinson's Disease and Movement Disorders.

"Perhaps estrogen holds the key to why women develop Parkinson's disease less often and are at a lower risk for it than men," said Demetrius Maraganore, M.D., associate professor of neurology at Mayo Clinic and Mayo Foundation, Rochester, MN.

In a preliminary study, Dr. Maraganore and fellow researchers found postmenopausal women on hormone replacement therapy (HRT) were less likely to have Parkinson's disease than those who were not on the therapy, suggesting estrogen may help protect against development of the disease.

The interest in the estrogen/Parkinson's connection has been piqued by research in recent years showing estrogen may be a protective factor in Alzheimer's disease, a neurological disorder that has many similarities to Parkinson's.

In related studies:

-- Postmenopausal women with Parkinson's Disease who had taken HRT scored 16 percent higher on long-term verbal memory tests than those who had not had HRT, according to a study conducted at the University of Utah School of Medicine.

-- National Institutes of Health (NIH) researchers found that the estrogen in hormone replacement therapy may actually increase absorption of the Parkinson's disease drug therapy levodopa, in contrast to previously accepted thought that HRT interfered with absorption of the drug.

-- Higher levels of naturally occurring estrogen may protect some people from Parkinson's disease, a University of Miami study suggests.

"All these studies are scratching at the surface, but they begin to paint a picture of the benefits of estrogen on Parkinson's disease," said Lisa Shulman, M.D., assistant professor of neurology at the University of Miami School of Medicine.

Six (eight percent) of 72 postmenopausal women with Parkinson's disease had been on HRT for six months or more, versus 10 (14 percent) of 72 women with no Parkinson's Disease, according to the Mayo Clinic study. Ranging in age at menopause from 30 to 56 and located through the Rochester Epidemiology Records Linkage system, each of the 72 postmenopausal women with Parkinson's disease were individually age matched with 72 postmenopausal women who did not have Parkinson's. Researchers then compared the numbers in each group who had been on HRT for different lengths of time.

"No matter how we defined estrogen use, it was less common in Parkinson's disease patients than in the control group," Dr. Maraganore said. "The next step is to do a large, multicentre study, but we definitely see a trend."

Mayo researchers also found that women with Parkinson's disease were three times more likely to have had hysterectomies than women who did not have the disorder, suggesting that the loss of naturally occurring estrogen is a risk factor. Although not all of the women who had hysterectomies had their ovaries removed, the surgery is often warranted when those organs do not function normally or produce estrogen, resulting in uterine dysfunction, note researchers.

In another study, 12 women with Parkinson's disease who were on or had been on postmenopausal hormone replacement therapy scored an average of 16 percent higher on long-term verbal memory tests than nine women who had not been on HRT, according to University of Utah researchers.

"Our research suggests hormone replacement therapy may benefit verbal long-term memory, without necessarily affecting other Parkinson's symptoms adversely," said Perla Thulin, M.D., assistant professor of neurology at the University of Utah School of Medicine, Salt Lake City. "Estrogen has been reported to enhance verbal memory in healthy postmenopausal women, so the beneficial effect may not be specific to Parkinson's, but could be particularly helpful for those with a disease that can affect memory."

The 21 postmenopausal women with Parkinson's disease were subjected to a four-hour battery of tests that measured arm and hand speed and dexterity, as well as short- term and long- term verbal memory, auditory attention, visual-spatial skills and global cognitive function. An improvement in verbal long-term memory among patients on HRT was the only significant difference noted between the groups.

Nine of the women were on HRT at the time of the test, while three had been on it for years but no longer were. Both groups seemed to benefit from HRT, noted Dr. Thulin.

Contrary to anecdotal evidence in medical literature, an NIH study found that HRT may actually improve the benefit associated with levodopa, the standard Parkinson's disease drug therapy, rather than decrease its effectiveness. Researchers say HRT potentially may allow patients to use less of the drug, which has a number of side effects.

Levodopa is given to patients with Parkinson's to help them combat the disabling symptoms of the disease, including stiffness, tremor and slow movements. According to anecdotal evidence, some women with Parkinson's disease who went on oral HRT and who were also taking levodopa had noticed an increase in their symptoms.

In the double-blind, controlled NIH study, none of the eight women with Parkinson's disease who were given an estrogen patch noted a difference in the effectiveness of levodopa when given the drug intravenously. In fact, researchers found that five of the women required an average of 27 percent less levodopa to turn off their Parkinson's symptoms.

"At home, levodopa is taken in pill form, rather than intravenously, so we don't know whether these women will generally be able to take less of the oral medication," said lead investigator Pierre Blanchet, M.D., formerly with the NIH and currently assistant professor of neurology of the University of Montreal Medical School in Quebec. "But perhaps it is possible to decrease the dosage. Decreasing the dosage may reduce the incidence of sudden jerky movements, called dyskinesia, experienced by many people who have been on levodopa for a while."

The women served as their own controls, each of them on an estrogen patch for two weeks and a placebo for two weeks, with two weeks off in between. The women also kept diaries to report their symptoms.

Thanks to The Doctor's Guide to the Internet™ for the article