Obesity Surgery

, Volume 29, Issue 4, pp 1185–1194 | Cite as

The Impact of Roux-en-Y Gastric Bypass on Bone Remodeling Expressed by the P1NP/βCTX Ratio: a Single-Center Prospective Cohort Study

  • Markus K. Muller
  • Daniel Gero
  • Daniela Reitnauer
  • Diana Vetter
  • Dilmurodjon Eshmuminov
  • Thorsten Hornemann
  • Marco BueterEmail author
Original Contribution



Bariatric surgery seems to decrease bone mineral density and increase the risk of fatigue fractures. P1NP (bone formation) and βCTX (bone resorption) were recently validated as reference bone turnover markers (BTM).


To assess changes in bone remodeling in severely obese patients undergoing Roux-en-Y gastric bypass (RYGB) by using a new composite biomarker, the P1NP/βCTX ratio.


We prospectively collected blood samples preoperatively, at 1 month and at 1 year from 114 consecutive RYGB patients from 12/2012 to 04/2014. Repeated measures ANOVA and multiple regression were used for data analysis. Cumulative incidence of fractures was assessed in 06/2018.


The P1NP/βCTX ratio decreased significantly (P < 0.001) from baseline to 1 month and 1 year (180 ± 6.6, 110 ± 4.1, and 132 ± 5.4). The 1-year P1NP/βCTX ratio did not correlate with BMI or ΔBMI, but inversely correlated with age (r = − 0.23, P = 0.014) and with hsCRP (r = − 0.26, P = 0.009), even after adjustment for age, sex, BMI, and lifestyle, and linearly correlated with albumin (r = 0.2, P = 0.037). At baseline, none of these correlations were detectable. Serum for all time-points was available from > 94% of the patients. At a median follow-up of 4.7 years, 8 patients (7.3%) had a bone fracture, all of them traumatic.


Following RYGB, bone remodeling increases, with a shift toward degradation. This effect seems to be weight-loss independent and shows a correlation with age, with the level of systemic inflammation, and with nutritional state. The risk of fractures should be assessed systematically in bariatric patients and measures of prevention should be improved accordingly.


Bone remodeling Roux-en-Y gastric bypass Parathyroid hormone P1NP/βCTX ratio Bone turnover markers Vitamin D Systemic inflammation 



We are grateful to Lilian Roth, MD, for her help in the data collection process.


The Best Oral Presentation Prize was awarded to Daniel Gero for presenting this study at the 8th International Federation of Surgery of Obesity – European Chapter meeting in Athens, Greece on 19th May 2018.


The study was entirely funded by the assistant-professorship research grant awarded by the University of Zurich to Prof. Dr. med. Marco Bueter, PhD.

Compliance with Ethical Standards

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and cantonal research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

All enrolled patients provided written informed consent for voluntary participation in the study and to de-identified use of their health-related data for scientific purposes.

Conflict of Interest

The authors declare that they have no conflict of interest.

Supplementary material

11695_2018_3640_MOESM1_ESM.pdf (280 kb)
ESM 1. Receiver Operating Characteristic curves to assess positive and negative predictive values of the burn turnover markers to predict a fracture after RYGB. A. P1NP at baseline (P = 0.379) and at 1-year (P = 0.02, AUC = 0.75, threshold = 80.4 ng/ml, specificity = 0.63, sensitivity = 0.88), B. ßCTX at baseline (P = 0.519) and at 1-year (P = 0.255), C. P1NP/ ßCTX at baseline (P = 0.041) and at 1-year (P = 0.159). (PDF 280 kb)


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of SurgeryCantonal Hospital FrauenfeldFrauenfeldSwitzerland
  2. 2.Department of Surgery and TransplantationUniversity Hospital ZurichZurichSwitzerland
  3. 3.Institute of Clinical ChemistryUniversity and University Hospital of ZurichZurichSwitzerland

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