The relationship between serum superoxide dismutase and thyroid function in obese patients after Laparoscopic sleeve gastrectomy

To investigate the cross-sectional and longitudinal correlation between serum superoxide dismutase (SOD) levels and thyroid function with obesity before and after laparoscopic sleeve gastrectomy (LSG). Patients with morbid obesity (n = 219, 112 males and 107 females) who underwent LSG were selected and they were subdivided into normal levels of SOD (NSOD, n = 112) and high levels of SOD (HSOD, n = 107) according to the median value of SOD levels (183 U/mL). SOD and thyroid hormones were measured and compared at baseline, 3, 6, and 12 months after LSG. The HSOD group had lower body mass index (BMI), total thyroxine (TT4), and thyroid-stimulating hormone (TSH) than the NSOD group (p < 0.001, p = 0.031, p < 0.001, respectively). However, they had higher free triiodothyronine (FT3) and free thyroxine (FT4) (p = 0.019 and p = 0.017, respectively). SOD was significantly negatively associated with TSH and positively associated with FT4. Of all the patients, 22.31% (NSOD: 66.67%; HSOD: 33.33%) had subclinical hypothyroidism (SH), and there were lower SOD levels in the SH group. Preoperative SOD was a protective factor for SH. After LSG, SOD and FT4 levels were increased at 12 months after LSG, however, TSH, FT3, total triiodothyronine (TT3) and TT4 levels decreased compared to the preoperative levels at 3, 6, and 12 months in the SH group. Postoperative changes in FT4 and TT4 levels correlated with changes in SOD levels. SOD, which is correlated with thyroid hormones, protects against SH in patients with obesity. The improvement in thyroid function with SH after LSG may be related to increased SOD levels.