In logistic regression, age (10-year increments, odds ratio [OR] 1.07 [1.02–1.11], p<0.01), diabetes (OR 1.33 [1.17–1.51], p<0.001), serum PO4 levels (0.1 mmol/l increments, OR 0.92 [0.91–0.94], p<0.001) and serum Ca levels (0.1 mmol/l increments, OR 1.23 [1.19–1.27], p<0.001) were independent predictors of PTH levels <120 pg/ml (Table 2). This evidence concerns the gene PTH and diabetes mellitus.