PTH and secondary hyperparathyroidism: PTH: Parathyroid hormone; CRF: Chronic renal failure; ESRD: End-stage renal disease; PTH: Parathyroid hormone; SHPT: Secondary hyperparathyroidism; HTRO: High-turnover renal osteodystrophy; iPTH: Intact parathyroid hormone; VDR: Vitamin D receptor.