Influence of vitamin D status on the variability of collagen I C-telopeptide in pre- and post-menopausal healthy women

Early predictive markers of bone resorption are required to plan intervention strategies ensuring a healthy aging. Collagen I C-telopeptide (CTX) as bone activity marker shows a fair biological variability, that cause the lack of a well-defined reference range. Given the wellestablished role of vitamin D in bone remodeling, the aim of this study was to assess the influence of vitamin D status on the variability of CTX serum levels in 131 pre-menopausal (45-54 years) and 951 post-menopausal women (55-90 years). Serum CTX and vitamin D levels were assessed, respectively, by ELISA and HPLC determination of 25-hydroxy-vitamin D3. A significantly negative dependence of CTX on vitamin D3, but not age, was found in the whole study cohort (B=-0.170, p<0.0001). A significantly negative correlation between CTX and vitamin D3 was found both in pre-menopausal (r=-0.2614; p=0.0061) and postmenopausal women (r=-0.2220; p<0.0001), and confirmed in post-menopausal women aged 55 to 59 years (r =-0.2840, p=0.0061), 60 to 64 years (r=-0.2143, p= 0.0129), and 70 to 74 years (r=-0.3078, p<0.0001). These findings suggest that vitamin D status determination and early vitamin D supplementation may be required in women at higher risk of bone resorption because of the physiologically reduced protective effects of estrogens.