Thus, the aims of our study were as follows: (1) to compare the prevalence of post-operative hypocalcemia associated with hypo-PTH (transient and permanent) after total thyroidectomy (TT) in patients with previous history of restrictive bariatric surgery (laparoscopic sleeve gastrectomy (LSG) and gastric binding (GB)) compared with a cohort of patients without; and (2) to compare the prevalence of post-operative hypocalcemia associated with hypo-PTH (transient and permanent) after TT in patients undergoing LSG compared to subjects undergoing to GB. This evidence concerns the gene PTH and Hypocalcemia.