Effect of sleeve gastrectomy on thyroid-stimulating hormone levels in morbidly obese patients with normal thyroid function

There are many studies, which demonstrate that morbid obesity is associated with an increase in Thyroid Stimulating Hormone (TSH) levels. However, the effect of Laparoscopic Sleeve Gastrectomy (LSG) procedure on postoperative TSH levels is not clear. This study aims to evaluate the effect of weight loss after LSG procedure on TSH levels in euthyroid patients with morbid obesity.

159 Euthyroid patients who applied for an LSG procedure (93.7% female, with a mean age of 34.18±10.01 years, BMI 43.2±6.82 kg/m2) were retrospectively analyzed for the study. The parameters used in the analysis were their serum free T3 levels (fT3), free T4 levels (fT4), and TSH levels preoperatively and at 6 months after surgery. The postoperative correlation between TSH and BMI (Body Mass Index), % EWL (Percent Excess Weight Loss), and % TWL (Total Weight Loss) levels were evaluated.

Mean BMI change from 43.2±6.82 kg/m2 to 30.48±5.63 kg/m2 (p<0.001), 6 months after LSG, was associated with a mean reduction in the TSH from 2.27±1.09 µU/dL to 1.61±0.99 µU/dL; p<0.001). Serum fT3 levels (3.23±0.42 ng/dL at baseline and 3.21±0.48 ng/dL at 6 months after surgery; p=0.409) remained steady. Serum fT4 levels (1.21±0.18 µU/dL at baseline and 1.43±0.20 µU/dL at 6 months after LSG; p<0.001) increased. Change in TSH was significantly correlated with change in BMI at 6 months after surgery (r=0.200, p=0.015). However, the decrease in TSH following LSG procedure did not correlate with % EWL (r=-0.114, p=0.159) and % TWL (r=-0.100, p=0.209).

After the LSG procedure, there was a significant decrease in TSH levels and a significant increase in fT4 levels, but no change was seen in fT3 levels. While this decrease in TSH levels showed a positive correlation with BMI, no statistically significant correlation was found with % EWL and % TWL.