Poster Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

Progressive increase in bone turnover despite improvement in markers of calcium homeostasis over twelve months post sleeve gastrectomy in obese subjects (#144)

Chris Kwan 1 2 , Anthony Russell 2 3 , Viral Chikani 2 3 , Anthony Cheng 2 4 , Chung Won 2 4 , Moe Thuzar 2 3
  1. Department of Internal Medicine, Princess Alexandra Hospital, Brisbane, Queensland, Australia
  2. Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
  3. Department of Endocrinology & Diabetes, Princess Alexandra Hospital, Brisbane, Queensland, Australia
  4. Department of Surgery, Princess Alexandra Hospital and Queen Elizabeth II Hospitals, Brisbane, Queensland, Australia

Introduction

Bariatric surgery, including sleeve gastrectomy, is associated with unfavourable effects upon bone health; the mechanism of which is unclear.1 The study aims to examine changes in calcium homeostasis and bone turnover over time after sleeve gastrectomy.

 

Methods

This is a single-centre retrospective cohort study involving 102 people (84 women) with mean±SEM age 42±2 years and baseline BMI 49.6±0.7kg/m2 who underwent sleeve gastrectomy between January 2015 and December 2016 and were followed for up to 12 months post-surgery under a multidisciplinary team. Data on changes in weight, serum markers of calcium homeostasis and bone turnover (P1NP) and hormone profiles were collected from electronic medical records, and analysed using repeated measures ANOVA.

 

Results

Body weight reduced significantly post-surgery (140.0±4.6 preop, 114.8±4.1 at 3 months, 106.2±4.0 at 6 months, 100.0±4.2kg at 12 months; P<0.001). P1NP significantly and progressively increased (48.7±8.4 pre-op, 59.5±8.2 at 3 months, 67.0±8.9 at 6 months, 68.1±8.9mcg/L at 12 months; P=0.001). Vitamin D levels significantly increased with supplementation of vitamin D (62±7 pre-op, 81±6 at 3 months, 79±8 at 6 months, 79±7nmol/L at 12 months; P<0.001), and parathyroid hormone levels significantly decreased (6.8±1.1 pre-op, 5.9±1.1 at 3 months, 5.8±0.9 at 6 months, 5.8±1.2pmol/L at 12 months; P=0.01) over 12 months post-surgery. Testosterone in men tended to increase (10.43±3.2 pre-op, 16.5±7.3 at 3 months, 18.3±5.1 at 6 months, 18.6±7.5nmol/L, P=0.12). There were no significant changes in serum calcium, phosphate, thyroid function or renal function over time. Gender did not significantly influence P1NP changes over time.

 

Conclusions

Bone turnover progressively increased over 12 months post sleeve gastrectomy, which likely contributes to the well-known adverse effect of bariatric surgery on bone health. This occurred despite improvement in calcium homeostasis and sex hormone profiles. Future studies need to focus on other mechanisms of increased bone turnover.

  1. Yu EW. Bone metabolism after bariatric surgery. J Bone Miner Res. 2014 Jul;29(7):1507-18. doi: 10.1002/jbmr.2226.