Serum total hydroxyproline assay: effects of age, sex and Paget's bone disease

An assay was developed for total hydroxyproline (protein, peptide and free) in 12 h fasted human serum. Values obtained from 80 adults judged normal by laboratory and physical examinations showed age and sex effects; values increased with age and were higher for men. Assay of serum samples from 22 patients with Paget's bone disease revealed values significantly above normal taking age and sex into consideration (p = 0.001). Serum alkaline phosphatase and serum hydroxyproline values for these patients were correlated (r = 0.91). Serum total hydroxyproline may be a useful assay for evaluating metabolic bone diseases but age and sex must be taken into consideration in the interpretation.