Thin bones: Vitamin D and calcium handling after bariatric surgery

Bariatric surgery has proven to be a valuable treatment option for morbid obesity. However, these procedures can lead to impaired intestinal absorption of calcium and vitamin D, thereby challenging calcium homeostasis and possibly contributing to bone loss leading to an increased fracture risk. Besides calcium and vitamin D malabsorption, hormonal changes occurring after surgery can also be the source of observed bone loss. In this review, first, a case report will be discussed, highlighting the relevance of this topic. Afterwards, changes in bone density and fracture risk, after the two most performed types of bariatric surgery, Sleeve Gastrectomy (SG) and Roux-en-Y Gastric Bypass (RYGB) will be discussed. In addition, we discuss the putative underlying mechanisms leading to bone changes based on both preclinical and clinical observations. Nonetheless, it is clear further research is needed to further elucidate the exact mechanisms of bone loss following bariatric surgery and subsequently identify potential treatment options for bone preservation.