[Age-related changes of urinary collagen crosslinks and serum osteocalcin in postmenopausal women]

Urinary collagen crosslinks, lysyl pyridinoline (LP) and hydroxy lysyl pyridinoline (HL), have been shown to be specific parameters of bone degradation, while serum osteocalcin, referred to as bone Gla-protein (BGP), has been used as a sensitive marker of bone formation. The current cross-sectional study was designed to compare between pyridinoline contents in initial fasting urine and serum BGP in postmenopausal women aged 50-90 years. Both LP and HL increased by around 20% and BGP increased by nearly 30% in a later stage of menopause, indicating the possibility that bone turnover did not decline with age as far as could be assessed by these chemical markers. It was of interest that significant correlations of pyridinoline to BGP in the 50s and 60s (r = 0.52 - 0.60, p < 0.05) became insignificant after age 70. Although there is a limitation to these biochemical markers, the present data indicate that the coupling mechanism between bone resorption and formation may become inefficient with aging in postmenopausal women.