Bone turnover markers in old vs early postmenopausal women

Abstract

Background and objectives: Osteoporosis has two distinct varieties described–post-menopausal and senile. We hypothesize that bone turnover markers may help distinguish between these two pathogeneses. Design and participants: A retrospective review of 976 fasting metabolic bone studies (FMBS) performed in an outpatient clinic identified 55 patients who met inclusion criteria. They were divided into the postmenopausal (age 50-65) and old-old (age 75 and above) groups. Measurements: We compared bone resorption (urinary N-Telopeptide/Creatinine (NTx/Cr)) and formation (Alkaline Phosphatase (ALP) and Procollagen type 1 N-terminal propeptide (P1NP) in the two groups using independent sample t-tests. Results: P1NP was significantly lower in the OO group (73.9 vs 41.6, p=0.037). There was no difference in ALP (88.7 vs 78.3, p=0.127) and NTx/Cr (40.0 vs 42.8, p=0.554). Conclusion: This study suggests that in PM osteoporosis bone formation is preserved with increased resorption. In senile osteoporosis there is reduced formation combined with high resorption suggesting uncoupling. This supports the hypothesis of senile vs postmenopausal osteoporosis being different in pathogenesis. This may be important in choice of treatments. P1NP is a good marker of formation, but ALP is not. Bone ALP may need study. NTx/Cr may be influenced by other physiological and bone factors.