Researchers aren’t sure why some people get Parkinson’s. In people with Parkinson’s, brain cells that produce the chemical messenger dopamine start to die. Dopamine send signals to the areas of the brain that deal with muscle activity and movement. The brain starts to lose the ability to tell the body when and how to move. Risk factors include having a relative with Parkinson's, being exposed to certain pesticides and herbicides, getting older, and lower levels of estrogen in women.