The effects of synbiotic supplementation on thyroid function in hypothyroid patients: a randomized, double‑blind, placebo‑controlled trial

Background and Objective: Hypothyroid disease, which is a major endocrine problem worldwide, characterized by impaired production of thyroid hormones. The metabolism of thyroid hormones has been linked with composition of gut microbiota. Limited evidences are available that demonstrated the efficacy of probiotic products on levothyroxine metabolism and thyroid hormones activity. Therefore, the purpose of this study was to investigate the effect of synbiotic supplementation on thyroid function through influence on gut microbiota in hypothyroid patients. Materials and Methods: This study was conducted as a randomized, double-blind, placebo-controlled trial among 60 patients with hypothyroidism. Participants were randomly recruited into two groups to receive either 500 mg/d of synbiotic supplementation (n=30) or placebo daily (n=30), 2 hours after levothyroxine tablet for 8 weeks. Thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), anti–thyroid peroxidase (Anti-TPO), levothyroxine dose (LT4 dose) were assessed at first and the end of intervention. All analysis were performed according to the Per-Protocol (PP) method, so only participants who completed the 8 week study period were entered into the analysis (compliance rate ≥ 90%). Findings: A total of 60 patients with hypothyroidism (5 males and 55 females) were enrolled at the beginning of this study. Finally, only 56 patients (29 in synbiotic and 27 in placebo groups) completed to the final analysis. Our findings presented, TSH concentration and LT4 dose were significantly decreased after the 8 weeks of intervention period in synbiotic group (P = 0.007, P = 0.017) while did not significantly change in compared with the placebo. In addition, FT3 variable at the end of intervention was significantly higher (P = 0.000) in both groups however these changes were not significant between two groups (P = 0.259). Moreover, we did not observe any statistically significant within or between groups in Anti-TPO variable (P > 0.05). Conclusion: We found taking synbiotic among hypothyroid patients for 8 weeks had beneficial effects on thyroid function in within group analysis, whereas did not have any effects on all variables in comparison to the placebo. Further studies with larger sample size and longer duration are needed to confirm this effect. Clinical Trial Registration: IRCT20121216011763N35

Keywords:

Hypothyroid , Thyroid function , Synbiotic supplementation