Gut Microbiota Alterations in Hypothyroidism: A Pilot Study Revealing Increased Abundance of Specific Bacterial Genera Publisher



Tavassol ZH ; Farsi F ; Ettehadmarvasti F ; Ejtahed HS ; Hasaniranjbar S
Source: Journal of Nutrition and Metabolism Published:2026

Abstract

Background: Hypothyroidism (HT) is a prevalent thyroid disorder characterized by insufficient thyroid hormone production, leading to metabolic complications. Emerging research suggests a link between gut microbiota and thyroid regulation, positing that alterations in gut bacterial populations may contribute to HT’s development and progression. This study aimed to investigate these associations by comparing gut microbiota compositions between individuals with HT and healthy adults, potentially refining diagnostic tools and therapeutic strategies. Methods: In this pilot study conducted between 2019 and 2023, 15 hypothyroid patients and 15 age- and gender-matched healthy controls participated in the study. Exclusion criteria were applied to eliminate confounding factors. Anthropometric data were collected, and stool samples underwent microbial analysis. Total bacterial DNA was extracted, and quantitative real-time PCR targeting 16S rRNA genes across eight bacterial genera was performed. The Mann–Whitney U test was used for statistical analyses. Results: No significant differences were observed in baseline demographic and anthropometric characteristics between groups. However, hypothyroid patients exhibited significantly elevated levels of Bacteroides, Bifidobacterium, Escherichia, Fecalibacterium, and Prevotella (p values < 0.001–0.030). No significant differences were found in levels of Akkermansia, Lactobacillus, or in the Bacteroides/Prevotella ratio. Conclusion: This pilot study provides preliminary indications of a possible role of gut microbiota in the pathophysiology of HT. Variations in bacterial composition suggest a significant influence of gut health on thyroid regulation. Future studies with larger cohorts are needed to explore the biological pathways linking the gut microbiome to thyroid function, which may lead to novel microbiota-targeted therapeutic approaches. Copyright © 2026 Zahra Hoseini Tavassol et al. Journal of Nutrition and Metabolism published by John Wiley & Sons Ltd.