Bone metabolism in Chinese patients after laparoscopic Roux-en-Y gastric bypass

Laparoscopic Roux-en-Y gastric bypass is a leading metabolic surgery for obese patients with type 2 diabetes mellitus. However, postoperative nutritional deficiencies and abnormal bone metabolism are possible. In this study, we investigated the mid-term impact on bone metabolism of laparoscopic Roux-en-Y gastric bypass.

This retrospective study involved 238 patients with type-2 diabetes mellitus and obesity who underwent laparoscopic Roux-en-Y gastric bypass in our institution; patients were followed for 3 years. Patients received a calcium supplement (1,200 mg per day), alfacalcidol (0.5 µg per day), and a multivitamin (1 tablet per day), postoperatively. We recorded and analyzed patients' body mass index, and blood levels of 25-hydroxy-vitamin D, calcium, and parathyroid hormone. Data for 16 patients 6 months postoperatively were selected randomly to evaluate bone-specific alkaline phosphatase and the bone resorption marker, C-terminal crosslinking telopeptide of type I collagen (CTX-1).

Of the 238 patients, 111 were women, and 127 were men (mean age: 46.91±12.03 years; mean body mass index: 31.37 kg/m²). 25-hydroxy vitamin D₃ levels did not change (P>0.05) compared with preoperative levels during the 3-year follow-up. Parathyroid hormone (PTH) levels increased (P<0.05), while serum calcium decreased (P<0.05). Patients' body mass index decreased sharply 3 months postoperatively (preoperative vs. postoperative mean: 31.37±3.52 vs. 25.60±2.86, respectively; P<0.05). We saw no decrease in 25-hydroxy vitamin D₃ levels with supplementation, postoperatively. CTX-1 and bone-specific alkaline phosphatase levels showed no significant changes comparing pre- and postoperative levels at 6-, 12-, and 24 months (P>0.05). However, CTX-1 levels increased in the first 12 months postoperatively, then decreased in the second year; bone alkaline phosphatase levels increased gradually.

Laparoscopic Roux-en-Y gastric bypass is effective for weight loss, but also has an impact on bone metabolism, which increases the risk of fracture. Our results highlight the importance of regular follow-ups and full-dose calcium and vitamin supplementation, postoperatively.