Parkinson's disease is a progressive neurodegenerative disorder affecting about 1 million people. Evidence indicates that Parkinson's disease patients are at a higher risk for low bone mineral density, which can contribute to increased fractures compared to healthy subjects. In fact, several risk factors of osteoporosis in patients with PD have been identified, including advanced stages of PD, low body mass index, inadequate sunlight exposure and decreased vitamin D levels. Some or all of these factors in conjunction with decreased immobilization that may occur with PD, put patients at increased risks for fractures. Few studies however have examined bone markers in PD patients. Even fewer studies have examined the impact of Vitamin D supplementation on bone metabolism and mineralization in PD patients.