Urinary excretion level of hydroxylysylpyridinoline as an index of bone resorption

Hydroxylysylpyridinoline (HP), an intermolecular cross-linking amino acid, is present only in bone and cartilage collagen. We examined urinary HP levels in order to assess bone collagen metabolism using HPLC. Urinary HP excretion levels (nmol/mmol creatinine) of healthy control groups gradually increased with aging. Urinary HP excretion levels of females were higher than those of age-adjusted males. On the other hand, the urinary excretion levels of HP in osteoporotic patients were significantly higher than those of age and sex-adjusted controls. It is suggested that the determination of urinary HP excretion levels is useful in the clinical evaluation of metabolic bone diseases, especially osteoporosis.