Changes in bone mineral density after sleeve gastrectomy or gastric bypass: relationships with variations in vitamin D, ghrelin, and adiponectin levels.

BACKGROUND: A major long-term concern after gastric bypass (GBP) is the risk of osteoporosis; however, little is known about this complication in patients undergoing sleeve gastrectomy (SG).

OBJECTIVE: To evaluate changes in bone mineral density (BMD) after GBP and SG, and its relationship with changes in vitamin D, parathyroid hormone (PTH), ghrelin, and adiponectin.

METHODS: Twenty-three women undergoing GBP (BMI 42.0 ± 4.2 kg/m2; 37.3 ± 8.1 years) and 20 undergoing SG (BMI 37.3 ± 3.2 kg/m2; 34.2 ± 10.2 years) were studied before and 6 and 12 months after surgery. BMD was measured by dual-energy X-ray absorptiometry. Plasma PTH, 25-hydroxyvitamin D (25-OHD), ghrelin, and adiponectin concentrations were determined. Food as well as calcium and vitamin D supplement intake was recorded.

RESULTS: Excess weight loss (mean ± SE), adjusted by baseline excess weight, was 79.1±3.8% and 74.9 ± 4.1% 1 year after GBP and SG, respectively (p = 0.481). Significant reduction in BMD for total body (TB), lumbar spine (LS), and femoral neck (FN) was observed after GBP. In the SG group, reduction in BMD was significant only for TB. Adjusted by baseline BMD, the difference between change in BMD for GBP vs. SG was not significant for TB, LS, or FN. Percent reduction in ghrelin concentration was a main factor related to total BMD loss (GBP group) and LS BMD loss (GBP and SG groups).

CONCLUSIONS: One year after gastric bypass, bone mineral density was significantly affected, mainly at the femoral neck. Decreases in bone mineral density were more dramatic among patients who had greater baseline BMD and greater reduction in ghrelin concentrations.