PTH and secondary hyperparathyroidism: No differences were found in serum calcium, 25(OH) vitamin D, ALP and creatinine in both groups, but FD patients had significantly higher PTH levels compared to controls (p = 0.016); moreover, 5 patients with FD (35.7%) and 3 controls (7.1%) presented secondary hyperparathyroidism (p = 0.015).