New research from Rush University Medical Center is the first to directly tie testosterone levels in men to the onset of Parkinson’s disease and to the rapid development of symptoms. This is the first reliable model of the development of Parkinson’s disease using animals. The research was published in the Journal of Biological Chemistry.
Parkinson’s disease classically affects more men than women and usually makes its appearance after 60 years of age.
While doctors and scientists know that a decrease in the creation of a neurotransmitter called dopamine in the substantia nigra (an area of the midbrain) is responsible for the common symptoms of Parkinson’s disease including initial trouble with walking, slowness of movement, shuffling gait and the advanced symptoms of dementia and depression, the real cause remains unknown to date.
The researchers, led by Dr. Kalipada Pahan, are the first to make establish a direct correlation between testosterone levels and the onset of Parkinson’s disease. The scientists have also discovered that one testosterone chemical that is naturally produced can relieve the symptoms of Parkinson’s disease in the early stages by restoring the supply of dopamine that produces the symptoms of Parkinson’s disease in men.
The researcher initially castrated a test group of mice. The mice developed the classical early stage symptoms of Parkinson’s disease. Feeding the castrated mice a testosterone replacement in their food restored the castrated mice to full function with no symptoms of Parkinson’s disease. The 5-alpha dihydrotestosterone used in the mouse’s food is one of the male sex hormones that are responsible for the initiation of secondary sex characteristics in men like facial hair. The compound has also been associated with male pattern baldness and replacement therapy using this hormone has been successful in hair restoration.
The researchers also found that nitric oxide synthase (a hormone involved with neural signaling and neurotransmission) and nitric oxide levels increased dramatically in castrated mice. Mice that were genetically altered to be incapable of reacting to the effects of nitric oxide synthase did not show signs of the development of Parkinson’s even when castrated.
The research established a direct link between testosterone levels and Parkinson’s disease development and progression in men. Testosterone levels decline with age. The correlation is substantiated by the typical onset of Parkinson’s disease in men after the age of 50. Lower testosterone levels are also responsible for loss of muscle tone and strength that may be associated with Parkinson’s disease symptoms.
This is the first research that establishes a direct link between a natural process (testosterone depletion with age) and the onset of Parkinson’s disease. The research also is the first to identify the chemical that is most probably the cause of the reduction in dopamine levels that causes Parkinson’s disease in men.
The scientists are presently testing existing testosterone replacement therapies that have already been FDA approved as well as 5-alpha dihydrotestosterone therapy that is also FDA approved as a potential preventative and possible cure for Parkinson’s disease in men.