Statistical Analysis
Statistical analysis was performed by the SPSS version 20.0 (IBM, Armonk, New York, United States). The normality of distribution was examined by using both the Shapiro-Wilk W test. Descriptive statistical methods, including percent and mean ± standard deviation(SD) or median (interquartile range[IQR]), were used to provide the basic features of the data. Mann-Whitney U test was used for non-normally distributed continuous variables for normal PTH levels group and secondary hyperparathyroidism group. A p-value less than 0.05 was accepted as significant.