Background: PARATHYROID hormone (PTH) levels can make changes in serum biomarkers and affect progression symptoms of many diseases. One of these is Parkinson’s disease (PD) and according to previous studies, it seems that PARATHYROID gland function is effective in severity of symptoms of PD. This study aimed to explore the role of PTH in PD progression regarding the lack of researches in this field in the Middle East.Methods: This case-control study was carried out in Alzahra hospital in Isfahan, Iran.125 patients with PD, diagnosed by experienced neurologists and 112 healthy controls matched for age and gender with patient group were asked to participate during September to November 2011. At baseline, the severity of PD was evaluated with motor part of the Unified Parkinson’s Disease Rating Scale III (UPDRS III). The level of PTH, calcium, phosphorus, and 25-hydroxy vitamin D were measured.Findings: The mean±SD of PTH level was significantly lower in patients group (45.2±18.8 IU/l) compared to controls (70.8±28.5 IU/l) (P=0.0001); there are not any significant correlation between hormone level, elements and severity of PD. We observed that men had more risk of PD than women (Odds ratio=2.53, [CI: 1.27‑5.03], P: 0.0080).Conclusion: This study could not confirm the relationship between the level of PARATHYROID gland function, the level of serum PTH and severity of motor symptoms in PD. It could be explained by the lack of a sufficient number of Hypo and hypercalcemia, phosphatemia and Hypo-or hyperPARATHYROIDism in our samples.