Endocrine Abstracts

Aim: The study aimed to investigate the relation between the levels of the bone formation marker P1NP and the risk of subsequent hip fractures in elderly women.

Materials and methods: Women born 1924–27 who participated in two population-based health studies in Bergen (The Hordaland Health Study (HUSK) 1997–2000) and in Oslo (The Oslo Health Study (HUBRO) 2000–2001), were followed up regarding hip fractures from date of inclusion until end of 2007 in HUBRO and until end of 2008 in HUSK. Serum P1NP was determined by Multigamma RIA kit (Orion Diagnostica, Espoo, Finland) at the Hormone Laboratory at Oslo University Hospital, in serum samples collected at baseline and stored at −80 °C. The study was designed as a case-cohort study, including identified hip fracture patients (n=306) and a random sample of 9% of women in the same cohorts (n=311). Cox proportional hazards regression with inverse probability weighting and robust variance with serum P1NP as explanatory variable was performed.

Results: P1NP levels ranged from 7 to 127 ng/ml. A U-shaped relation between P1NP and hip fracture was suggested. Compared to the lowest quartile of P1NP, the hazard ratio (HR) in the 2nd quartile was: 0.68 (95% CI: 0.42–1.09), in the 3rd quartile: 0.77 (95% CI: 0.49–1.22), and in the 4th quartile: 1.04 (95% CI: 0.66–1.63). Adjusting for covariates or excluding participants using medication known to lower P1NP did not substantially alter the results. A confirmatory spline analysis showed a significant U-shaped relation.

Conclusion: A U-shaped relation between P1NP and hip fractures was found, suggesting both low and high levels of P1NP confer increased risk of osteoporotic fractures. Whether the fracture risk among those with the lowest P1NP levels is mediated through generally low bone turnover, or isolated impaired osteoblast collagen synthesis, remains to be elucidated.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.