Impact of Bariatric Surgery on Thyroid Morphology and Thyroid Function

Few studies have evaluated the impact of bariatric surgery (BS) on thyroid function and morphology, and how it correlates to inflammatory and metabolic markers. We aimed to evaluate all those parameters together.

A longitudinal study included 70 patients with severe obesity. The bariatric group (BG) enrolled 40 patients who underwent BS, and the control group (CG) enrolled 30 patients who did not undergo BS. Both were submitted (pre- and 2nd-year) to thyroid ultrasound and laboratory analyses to determine the levels of thyroid hormones, inflammatory, and metabolic markers.

Thyroid volume (TV) decreased after BS (-1.5 cm³), differing significantly from the CG (+0.6 cm³; p = 0.003). ΔTV was independently and positively correlated with ΔHOMA-IR (0.41 (0.11/7.16) p = 0.007) and ΔIL6 (0.02 (0.01/0.3) p = 0.016). A nonsignificant correlation between ΔTV and ΔBMI was detected (0.38 (-0.01/0.09) p = 0.152). We also observed a negative correlation between ΔTV and ΔTSH (-2.03 (-2.87/-1.19) p = 0.000) and ΔT3/T4 ratio (-0.06 (-0.09/-0.02) p = 0.001). TSH had a nonsignificant reduction with BS (-0.3872 vs. -0.2483 p = 0.128). The conversion of T4 to T3 had a significant increase after BS, as demonstrated by the T3/T4 ratio (+5.16 p = 0.01). Despite an increase in the prevalence of thyroid nodules in the BG, it was not statistically significant (p = 0.340).

BS was associated with a reduction in TV and a nonstatistically significant reduction in TSH. The variations in TV were related to the metabolic markers and inflammatory changes. An increase in the conversion of T4 to T3 with BS was detected, possibly related to inflammatory improvement.