Urine products of bone breakdown as markers of bone resorption and clinical usefulness of urinary hydroxyproline: an overview.

Abstract

Urinary hydroxyproline has been in use as a marker of bone resorption, but it lacks sensitivity and specificity. It is a modified amino acid that is a metabolic product of collagen breakdown. Hydroxyproline may be released either free or with fragments of the collagen molecule attached during bone resorption, and it is also liberated by the breakdown of complement and nonskeletal collagen.