Hypocalcaemia following thyroidectomy among patients who have previously undergone bariatric surgery: systematic review and meta-analysis

Lay Summary Low calcium levels are a common complication after surgical removal of the thyroid gland. Patients who have had weight loss surgery (bariatric surgery) have altered calcium metabolism and are prone to low calcium levels. This study assessed whether previous weight loss surgery increased the risk of low calcium levels after thyroid surgery. A search was made of previously published studies assessing the relationship between previous weight loss surgery and low calcium levels after thyroid surgery. Studies have shown that previous weight loss surgery makes patients more than three times more likely to have low calcium levels after thyroid surgery. Management of low calcium in these patients is more challenging than in patients who have not had weight loss surgery. Surgeons performing thyroid surgery need to be aware of whether a patient has previously had weight loss surgery as they have an increased risk of low calcium after thyroid surgery. Background Hypocalcaemia is a common complication after thyroidectomy. Bariatric surgery is associated with significant changes in calcium metabolism. Some studies have identified bariatric surgery as a risk factor for hypocalcaemia after thyroidectomy. This systematic review and meta-analysis assessed whether a history of bariatric surgery was associated with an increased risk of hypocalcaemia after thyroidectomy. Methods This prospectively registered systematic review (PROSPERO; CRD42021295423) was performed in accordance with PRISMA guidelines. Meta-analysis was undertaken using the Mantel-Haenszel method, with outcomes reported as ORs with 95 per cent confidence intervals. Results Twenty studies were included in the qualitative synthesis. Five studies incorporating 19 547 patients met the inclusion criteria for meta-analysis, of whom 196 (1.0 per cent) had a history of bariatric surgery. Patients with a history of bariatric surgery were more likely to develop hypocalcaemia after thyroidectomy (30.6 versus 13.0 per cent; OR 3.90, 95 per cent c.i. 1.50 to 10.12; P = 0.005). Among those with a history of bariatric surgery, patients who underwent a bypass procedure were more likely to develop hypocalcaemia after thyroidectomy than those who had a restrictive procedure (38 versus 23 per cent; OR 2.12, 1.14 to 3.97; P = 0.020). Conclusion Patients with a history of bariatric surgery have a significantly greater risk of hypocalcaemia after thyroidectomy, with a heightened risk among those who have had a bypass procedure. Surgeons performing thyroid surgery should be aware of the increased risk of hypocalcaemia after thyroidectomy among these patients. This systematic review and meta-analysis has shown that patients with a history of bariatric surgery have a greater than three times increased risk of hypocalcaemia after total thyroidectomy. The management of hypocalcaemia among patients with a history of bariatric surgery is challenging, with many developing refractory hypocalcaemia and measures as extreme as bariatric surgery reversal trialled. Further work is needed to devise a personalized approach to the management of post-thyroidectomy hypocalcaemia in this population.