RESUMOObjetivo: Avaliar a alteração de peso durante o tratamento do hipertiroidismo e correlacioná--la com IL-6 e TNF-alfa. Sujeitos e métodos: Quarenta e dois pacientes foram incluídos. Peso corporal (PC), índice de massa corpórea (IMC), características clínicas e laboratoriais foram registrados. IL-6 e TNF-alfa foram determinados antes do tratamento com metimazol (MMI) e no estado de eutiroidismo. Resultados: O PC foi de 59,62 ± 11,5 kg no estado de hipertiroidismo e de 69,91 ± 14,4 kg no estado de eutiroidismo (p < 0,001 Descritores Hipertiroidismo; fator de necrose tumoral alfa; interleucina-6; metimazol; hormônio tiroidiano; peso corporal ABSTRACT Objective: To evaluate weight change during hyperthyroidism treatment, and to correlate it with IL-6 and TNF-alpha concentrations. Subjects and methods: Forty two patients were included. Body weight (BW), body mass index (BMI), clinical and laboratory characteristics were recorded. IL-6 and TNF-alpha were determined before treatment with methimazole (MMI) and in euthyroidism. Results: BW was 59.62 ± 11.5 kg in hyperthyroidism, and 69.91 ± 14.4 kg in euthyroidism (p < 0.001). BMI increased from 23.1 ± 3.8 kg/m 2 to 27 kg/m 2 ± 4.7 during treatment (p < 0.0001). Before treatment, 66.6% subjects had BMI < 25 kg/m 2 and 33.3%, BMI ≥ 25 kg/m 2 . In euthyroidism, 38% of patients had BMI < 25 kg/m 2 and 62%, BMI ≥ 25 kg/m 2 (p = 0.01). In euthyroidism, we found a significant reduction in IL-6 and TNF-alpha concentrations, but no correlation between IL-6 and TNF-alpha, and BW or BMI. Conclusion: An important increase in BW and BMI was observed during hyperthyroidism treatment, and IL-6 and TNF-alpha alterations were only related with return to euthyroidism. Arq Bras Endocrinol Metab. 2012;56(6):364-9