Effect of Laparoscopic Sleeve Gastrectomy vs. OAGB on Thyroid Function Tests in Patients with Morbid Obesity and Subclinical or Clinical Hypothyroidism

Purpose As one of the major problems for the health sector, morbid obesity is associated with many hormonal dysfunctions, including thyroid hormone disorders. Few studies have been performed on improving subclinical and clinical hypothyroidism following bariatric surgery. Therefore, we designed and conducted this study to evaluate the effect of various types of bariatric surgery on thyroid hormone levels and to assess the change of levothyroxine requirement in these patients. Methods The data of all patients who underwent either sleeve gastrectomy (SG) or one-anastomosis gastric bypass (OAGB) surgery in the 5 years from 2016 to 2020 at our hospital were analyzed retrospectively. Results From 1486 patients (792 cases of SG and 694 cases of OAGB), 281 patients had preoperative abnormal thyroid function tests: subclinical hypothyroidism (102 patients) and clinical hypothyroidism (179 patients). The T4 level did not change significantly in any of the groups and subgroups. However, the TSH level at the end of the sixth month after SG and OAGB in both groups significantly lowered. Nevertheless, there is no significant difference between the effect of SG and OAGB surgical procedures on the rate of TSH and T4 alterations in both subclinical and clinical hypothyroid patients. In the sixth month after surgery, 49% of clinically hypothyroid patients in the SG group (n = 179) reduced or stopped taking the medication. Conclusion Whereas bariatric surgery reduces TSH levels, it does not significantly alter T4 levels. Furthermore, there is no apparent difference between subclinical and clinical hypothyroidism and different types of bariatric surgery.