Monitoring PTH, vitamin D, calcium and phosphorus in patients with endemic nephropathy hemodialysis. Introduction: Endemic nephropathy is a chronic kidney tubulointerstitial disease and it has a progressive course and leads to chronic renal failure. In Croatia, the disease occurs in 14 villages of Brod-Posavina County. The causative agent of endemic nephropathy is Aristolochia lutea, the plant, which is located in the fields of wheat and whose toxicity originates from aristolochic acid. Objectives: The objective of the research is monitoring the metabolic changes of bone turnover in patients with endemic nephropathy. The monitoring of calcium, phosphorus, vitamin D, and PTH serum concentrations determines the correlations between the measured concentrations. In dialysis patients, PTH is usually increased while vitamin D levels are decreased, on the other hand, calcium and phosphorus are held within the reference value due to appropriate drug therapy. Study Design: Case control study Participants and methods: All patients are from the Brod-Posavina County area, and they are treated by dialysis at the General Hospital in Slavonski Brod. The group with endemic nephropathy included 27 patients, and the control group comprised 60 patients with other renal diseases.. Results: The average age of the patients is 65 years and both sexes are equally represented. In group of patients with endemic nephropathy, statistical methods have confirmed that longer dialysis treatment heighten the concentration of calcium, where in the control group longer dialysis treatment was related to vitamin D concentration. The longer duration of dialysis is proportional with increased PTH values. Higher average age is associated with a lower concentration of phosphorus. Conclusion: Endemic nephropathy is a disease specific to the Brod-Posavina County. These results have statistical significance, but the limiting factor is a small sample of 27 patients with endemic nephropathy. Longer duration of dialysis confirms that the measured serum concentrations show a higher degree of secondary hyperparathyroidism. Vitamin D values are significantly decreased. Replacement therapy successfully maintains the concentration of calcium and phosphorus within normal parameters.