Exploring the threshold relationship between PTH level and P1NP level in patients with osteoporotic fractures: a retrospective cross-sectional study

Abstract

Background

PTH plays a crucial role in bone remodelling by regulating bone formation. Pre-collagen type 1 N-terminal peptide (P1NP) is a key biomarker indicative of new bone formation. However, the relationship between PTH levels and P1NP levels in patients with osteoporotic fractures (OPFs) has not been fully elucidated.

Methods

This study analyzed data from 588 OPFs patients hospitalized between January 2015 and March 2022. Serum P1NP concentration serve as the dependent variable, while PTH level serve as the exposure variable. Covariates included age, gender; Charlson comorbidity index (CCI), body mass index (BMI), lymphocyte, neutrophil, monocyte, low-density lipoprotein (LDL), platelet, triglyceride, albumin, hemoglobin. Generalized estimating equations were used to assess the independent association between PTH and P1NP levels, adjusting for covariates. Non-linear relationships were evaluated using generalized additive models.

Results

This study found a positive association between PTH level and P1NP level in patients with OPFs (β = 0.59; 95% CI [confident interval] = 0.22 to 0.96; P = 0.0018). This association remained significant after multivariate adjustment. Moreover, the nonlinear model showed a threshold effect, with PTH level below 16.63 (pg/mL) being positively correlated with P1NP (β = 1.69; 95% CI = 0.90 to 2.47; P < 0.0001). However, this correlation did not hold true for PTH level above 16.63 (pg/mL) (β = 0.37; 95% CI = -0.34 to 1.07; P = 0.3091).

Conclusion

This study identified an inflection point and a nonlinear, threshold effect in the relationship between PTH and P1NP levels. Further research is needed to confirm these findings.