Abnormally low dopamine levels are the primary cause of Parkinson's disease, explains Medical News Today. When dopaminergic neurons in the brain's substantia nigra are severely impaired or fail to produce dopamine, a patient can experience difficulties in controlling his movements or coordination.
As of 2015, the exact causes of Parkinson's disease are unknown, but several factors can lead to the condition, including specific environments, occupations, genetics and Lewy bodies, according to Healthline. About 15 to 25 percent of patients with Parkinson's disease also have relatives with the same condition. Those who have a sibling or a parent with Parkinson's are four to nine times more likely to develop the disease than someone with no first-degree relatives who have the condition. Exposure to chemicals, such as Agent Orange, insecticides, fungicides and herbicides, has also been linked to Parkinson's. Lewy bodies, or groups of proteins located in the brain stem, contribute to motor coordination issues in those with Parkinson's.
The loss of nerve endings that produce a neurotransmitter called norepinephrine is also linked to Parkinson's disease, explains the National Institutes of Health. Norepinephrine is the primary messenger of the sympathetic nervous system, the part of the body that controls automatic processes, such as blood pressure and heart rate. Mitochondria and free radicals can also contribute to the development of the condition.