The hydroxyproline content of plasma of patients with impaired renal function.

The plasma concentration of hydroxyproline fractions were determined in 52 patients with diminished renal function. High levels were found in each case and a correlation was found between the serum creatinine concentration and the plasma concentrations of peptide-bound hydroxyproline. Bone biopsies was taken from 16 patients from renal insufficiency and the results of morphometric studies of the biopsies were correlated with the blood determinations. Free hydroxyproline levels correlated significantly both with bone formation and with bone resorption. However peptide-bound and protein-bound hydroxyproline levels did not correlate with bone histology. Hence the plasma concentration of free hydroxyproline in patients with renal insufficiency can be used as an index of bone collagen turn-over.