The effects of growth hormone (GH) therapy on biochemical markers of bone turnover were investigated in 11 short prepubertal children without GH deficiency by measuring serum osteocalcin, a marker for bone formation, and urinary concentrations of pyridinium cross-linked amino acids of collagen (PCL), and the peptide-bound pyridinoline residue N-telopeptide (NT), which are specific markers for bone resorption. GH treatment for three months increased bone turnover in this group of children: urinary PCL concentrations increased from 69 +/- 6.2 to 114 +/- 9.3 nmol/mmol Cr (p < 0.01), and urinary NT levels increased from 512 +/- 65 to 766 +/- 74 pmol BCE/mumol Cr (p = 0.058). Serum osteocalcin concentrations increased from 13.64 +/- 2.57 ng/ml to 26.45 +/- 1.39 ng/ml (p < 0.01). The increment in 12-hour urinary concentrations of PCL was highly correlated with the increment in 12-hour urinary NT levels (r = 0.92, p < 0.01). Stepwise multiple regression analysis revealed that the urinary concentrations of NT after 3 months of GH therapy were the best predictor of growth after 12 months of treatment (r = 0.78, F = 7.9, p = 0.037).