Analysis of pyridinoline, a cross-linking compound of collagen fibers, in human urine.

Pyridinoline, a cross-linking compound of collagen fibers, was found in human urine. A significant portion of urinary pyridinoline was in free form. The ratio of total pyridinoline to creatinine changed with age. It was high in children and decreased with growth. It was low and constant in adults, and increased slightly in old age. It was increased significantly in patients with certain bone and joint diseases. Urinary pyridinoline may serve as a useful marker for the breakdown of collagen fibers of skeletal tissues.