Change in Levothyroxine Requirements After Bariatric Surgery in Patients With Hypothyroidism.

Abstract

PurposeThis study aims to evaluate the need to modify the levothyroxine dose after surgery. Additional goals are to estimate the increase or decrease of total dose and weight-adjusted dose, assess the influence of weight loss on the levothyroxine requirements, and identify predictors.Material and methodsRetrospective study in patients with treated hypothyroidism that underwent bariatric surgery. The required levothyroxine dose was evaluated before the surgery and at 6, 12, and 24 months post-surgery. Dose modification during follow-up and its association with weight loss and other potential predictors were assessed. ResultsOf the 63 patients included, 82.54% needed an adjustment of dose during the follow-up. The total dose of levothyroxine decreased significantly at 6 months post-surgery (-49.1 µg/week; 95%CI= -93.7 to -4.5; p=0.031) and 12 months (-54.9 µg/week; 95%CI= -102 to -7.8; p=0.022), with no significant change at 24 months (p=0.114). The weight-adjusted dose increased at 6 months (1.37 µg/kg/week; 95%CI=0.91 to 1.83; p<0.001), 12 months (2.05 µg/kg/week; 95%CI=1.43 to 2.67; p<0.001), and 24 months (2.52 µg/kg/week; 95%CI=1.74 to 3.30; p<0.001). Weight loss showed significant association with weight-adjusted dose (OR=1.07; 95%CI=1.02 to 1.12; p=0.004) and did not with the total dose (p=0.320).ConclusionsIt is expected that the levothyroxine requirements change in the firsts years after bariatric surgery. This study shows a significant decrease in the total dose during the first year of follow-up and an increase in the weight-adjusted dose over the two first years. No predictors for the modification in the total dose of levothyroxine have been identified.