Figure 2 summarizes visually the changes occurring over time in bone turnover markers after bariatric surgery. Interestingly, the magnitude of variation in bone turnover markers is reportedly similar between diabetic and non-diabetic cohorts undergoing bariatric surgery, yet patients T2DM patients carry per se a higher risk of osteoporosis (122, 123). Because alterations in CTX and P1NP levels have also been reported in adolescents after RYGB (124) and SG (125), uncertainties remain on the final effect of bariatric surgery on bone mass peak and subsequent adult risk of osteoporosis. The gene discussed is CYP27A1; the disease is osteoporosis.