RESUMEN
INTRODUCTION: Nonthyroidal illness syndrome (NTIS) is common in hemodialysis patients (HPs). However, limited clinical trials have been conducted in this field. Therefore, the aim of this study was to investigate the effect of Se and/or N-acetyl-cysteine (NAC) on NTIS parameters in HPs. METHODS: In this factorial randomized controlled trial, 68 HPs were divided into four groups: group A received placebo of Se and NAC, group B received 600 µg per day of NAC and placebo of Se, group C received 200 µg of Se per day and placebo of NAC and group D received 200 µg of selenium and 600 µg of NAC per day for 12 weeks. Blood samples were taken at baseline and after 12 weeks to assess free tri-iodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), and reverse T3 (rT3) concentrations. RESULTS: Our finding demonstrated that rT3 levels were decreased in B, C, and D groups and increased nearly to baseline levels in the A group after 12 weeks, with a marked difference between the groups (p < 0.001) based on ANOVA. Although there were no significant differences in FT3 (p = 0.39), FT4 (p = 0.76), and TSH (p = 0.71) between the groups at the end of the trial. CONCLUSION: This trial showed that Se and/or NAC exert beneficial effects on rT3 levels in HPs. However, long-term clinical trials with a larger sample size using more appropriate biomarkers are recommended to evaluate the efficacy and safety of Se and/or NAC in HPs.