Women had higher levels of ‘striatal dopamine binding’ than men when the disease was first diagnosed. ‘Striatal dopamine binding’ simply means that women had more and better dopamine activity in their brains than did men when they were diagnosed with PD. In short, when women experience their first motor symptoms of PD their brains have a larger pool of effective dopamine receptors than do men when they are first diagnosed. The authors of the study suggest that female hormones like estrogen exert a protective effect for dopamine receptors. The authors also reported that the age of onset of symptoms in women was associated with indicators of estrogen status—things like age of menopause, number of children and duration of fertile life span. So perhaps estrogen activity helps to protect against the disease or delay its onset for women but once it appears the scientists found that the disease kills off the dopamine cells at similar rates in men and women. Presumably estrogen activity declines in women who get PD and once estrogen levels are low estrogen can no longer protect against the disease.
Source: Charlotte A Haaxma, Bastiaan R Bloem, George F Borm, Wim J G Oyen, Klaus L Leenders, Silvia Eshuis, Jan Booij, Dean E Dluzen, Martin W I M Horstink; Gender differences in Parkinson’s disease; J Neurol Neurosurg Psychiatry 2007;78:819–824.