Calcium metabolism, vitamin D and bone mineral density after bariatric surgery

Lower bone mineral density, vitamin D deficiency, lower lean body mass, greater loss of excess weight, and increased bone turnover are complications found after bariatric surgery correlated in the literature with increased risk of fractures. The prevention and treatment of such complications should begin immediately after surgery. The aims of the study were to evaluate bone mass in patients undergoing bariatric surgery by the Wittgrove technique after 1 year of the procedure and correlate it with body composition, weight loss, 25OH vitamin D levels, and markers of bone metabolism. The operated group (OG) participated in a clinical consultation; a blood sample taken and a body composition; and bone mineral density assessment by dual energy X-ray absorptiometry (DXA). The results were compared with a control group (CG). Fifty-six subjects in the OG and 27 in the CG were included. The bone mineral density (BMD), after the surgery, at the lumbar spine (LS) was lower in the OG than in the CG. There was a positive correlation between total body (TB) BMD with 25OHD, body mass index (BMI), and lean mass and an inverse correlation with percentage of excess weight loss (%EWL). Vitamin D deficiency was seen in 60.41 % (OG) and in 16.6 % (CG). PTH was higher in the OG, with secondary hyperparathyroidism in 41.7 %. In 26.5 % and 14.2 % of the OG, ALP and OC levels were above the reference values. In < 50 years, elevated values of carboxy-terminal telopeptide (CTX) were found in 66.7 % of patients. A difference was observed in the variation of CTX between 12 and 18 months when compared to over 24 months. Lower BMD was observed, correlated with lower lean body mass and greater loss of excess weight. Vitamin D deficiency with high prevalence of secondary hyperparathyroidism and high bone turnover was detected. The prevention of bone loss should be initiated in the first months after surgery, which is a period associated with severe muscle loss and increased bone turnover.