Is there a relationship between different types of prior bariatric surgery and post-thyroidectomy hypocalcemia?

Background: Hypocalcemia is a common complication after total thyroidectomy ( TT). A history of bariatric surgery has been identified as a risk factor for this complication. This study aimed to assess the risk of hypocalcemia post TT in patients with a history of obesity procedures: laparoscopic sleeve gastrectomy (LSG), Roux-en-Y gastric bypass (RYGB), and laparoscopic gastric banding (LAGB). Methods: We compared the risk of hypocalcemia post TT (serum calcium levels <8 mg/dL) between patients with restrictive (LSG and LAGB), malabsorptive (RYGB), and patients without a history of obesity surgery. Hypoparathyroidism was considered permanent if the plasma parathyroid hormone (PTH) levels at 6 months were less than 15 pg/mL (normal range: 15-65 pg/mL) and the patient still required oral calcium (calcium carbonate) and vitamin D supplementation, in addition to the supplements that were taken routinely before thyroidectomy. Results: From the 13,242 patients who underwent TT from 2006 to 2018, 90 patients (0.7%) had a history of bariatric surgery: 35 LAGB, 29 LSG, and 26 RYGB. The risk of hypocalcemia was higher in RYGB patients (50%, n=13) than in LAGB (17.1%, n=6) or LSG patients (20.6%, n=6) (P=0.003). Furthermore, hypocalcemia risk was similar between patients with a history of restrictive procedures (18.8%, 12/64) and patients with no history of bariatric surgery (17.2%, 2,268/13,152) (P=0.4). Permanent hypoparathyroidism was observed in one and 6 patients from the LAGB and RYGB groups, respectively; however, it was not observed in any patient from the LSG group. Conclusions: RYGB is a risk factor for hypocalcemia post TT, while restrictive bariatric procedures are not.