Urinary Hydroxyproline Excretion in Orthopedic Disease. Preliminary Report.

The significance of urinary hydroxyproline has not been completely clarified. It appears, however, that this amino acid excretion is correlated with either synthesis or destruction of collagen. Collagen hydroxyproline is reported to be formed by the irreversible hydroxylation of peptid-linked proline and no free hydroxyproline is incorporated directly into this protein. Therefore, the changes of collagen in the tissues can be indirectly measured by determining urinary hydroxyproline excretion. Although hydroxyproline has been variously studied concerning its significance in physiology and distribution in the tissues, metabolic study of this amino acid has been limited. Then, urinary hydroxyproline excretion in various orthopedic diseases was in· vestigated. The following observations have been made. Patients with severe bone lesion such as that arising from malignant bone tumor and primary parathyroid adenoma as well as those with congenital systemic bone disease were found in this study to excrete significantly increased amounts of hydroxyproline in the urine. This observation that hydroxyproline excretion is elevated in destructive bone tumor, in primary hyperparathyroidism, in rats receiving parathyroid extract, and in congenital systemic bone disease supports the view that the urinary hydroxyproline reflects the rapid rate of bone collagen degradation. At any rate, urinary hydroxyproline appears to be a good index of metabolic activity in bone diseases.