This report describes the serum osteocalcin values in children with mild to moderate, but relatively stable, renal dysfunction followed in the Growth Failure in Children With Renal Diseases Study. This report is derived from data obtained during the control period (6 months) before the initiation of vitamin D therapy. Up to three measurements per patient were obtained. Serum osteocalcin concentration was compared with creatinine clearance (glomerular filtration rate) calculated by the Schwartz formula; with serum concentrations of alkaline phosphatase, parathyroid hormone, and bicarbonate; and with the percentages of the recommended dietary allowances of calories and protein ingested. By standard correlation techniques, there appeared to be an inverse correlation between calculated creatinine clearance and serum osteocalcin concentration, and a direct correlation between serum osteocalcin and parathyroid hormone values. However, when we employed a statistical technique that takes into account repeated measures in the same patient, no correlation was found between calculated glomerular filtration rate and serum osteocalcin concentration, and no direct correlation was found between serum osteocalcin and parathyroid hormone values. The lack of a correlation between calculated glomerular filtration rate and serum osteocalcin values may be due to large fluctuations in the serum osteocalcin concentration, even though renal function is relatively stable.
Bibliographical noteFunding Information:
Osteocalcin is a bone-derived protein containing residues of the vitamin K-dependent amino acid 7-carboxyglutamic acid (bone Gla protein) and synthesized by osteoblasts) Supported by National Institutes of Health grants R01 DK 31370 and R01 DK 32431. Reprint requests: Aaron L. Friedman, MD, Department of Pediatrics, Clinical Science Center H4/472, 600 Highland Ave., Madison, WI 53792. 9/0/17215 Osteocalcin is found mainly in bone, but nanomolar concentrations circulate in the blood, and the circulating portion has been the focus of attention as a noninvasive measure of bone turnover. 2 We report on the serum osteocalcin levels in children with mild to moderate chronic renal failure who have not undergone dialysis, and we demonstrate the correlation (or lack thereof) between serum osteocalcin values and other biochemical or nutritional measurements that might affect or reflect bone turnover in patients with chronic renal failure.