Letters Bariatric surgery for obesity

Bariatric surgery: give more weight to bone loss

BMJ 2014; 349 doi: https://doi.org/10.1136/bmj.g6189 (Published 14 October 2014) Cite this as: BMJ 2014;349:g6189
  1. Michaël R Laurent, specialty registrar1
  1. 1Centre for Metabolic Bone Diseases, University Hospitals Leuven, B-3000 Leuven, Belgium
  1. michael.laurent{at}med.kuleuven.be

In their otherwise exhaustive review on bariatric surgery, Arterburn and Courcoulas fail to mention metabolic bone disorders among its complications.1 This is truly a missed opportunity, and I would like to draw attention to this problem.

It is a common misconception that obesity (which does not usually resolve after bariatric surgery) is protective for the skeleton. Several longitudinal studies show markedly increased bone turnover and considerable bone loss, especially at the hip, after malabsorptive procedures like Roux-en-Y gastric bypass, sleeve gastrectomy, and biliopancreatic diversion.2 3 The associated fracture risk remains unclear but may affect older (postmenopausal) patients most. The underlying mechanisms are incompletely understood. Decreased load bearing may contribute, although bone loss persists for years, despite the usual mild weight regain.2 3 Some patients develop osteomalacia due to calcium malabsorption, with or without vitamin D deficiency, and some develop secondary hyperparathyroidism. Metabolic acidosis, oxalosis, vitamin and trace element deficiencies, gut derived hormones, and microbiota may also play a role.2 3

In my experience, expertise in managing bariatric bone disease is often lacking. Many physicians are unfamiliar with the diagnosis of osteomalacia and the correct use of high dose calcium citrate, 25-hydroxyvitamin D3, or 1,25-dihydroxyvitamin D3. Calciuria and vertebral fracture assessments are probably more useful than current over-reliance on repeated dual x ray absorptiometry. Bisphosphonates also need to be used judiciously in this predominantly premenopausal population, and these drugs can precipitate hypocalcaemia in patients with an unrecognised calcium deficit. Guidelines mention that oral bisphosphonates can precipitate anastomotic ulcers and may be underabsorbed, but few specialists consider bone turnover markers to diagnose this potential cause of treatment failure.4

In summary, I urge bariatric teams to liaise with their local experts in metabolic bone diseases to review their follow-up, treatment, and referral protocols.

Notes

Cite this as: BMJ 2014;349:g6189

Footnotes

  • Competing interests: None declared.

References

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