Alterations in gut microbiota and fecal metabolites in euthyroid autoimmune thyroiditis during early pregnancy

Abstract Background and Objectives Euthyroid autoimmune thyroiditis (AIT) during early pregnancy has been linked to adverse pregnancy outcomes, yet the underlying mechanisms remain unclear. This study aimed to investigate the differences in gut microbiota (GM) composition and fecal metabolites between patients with euthyroid AIT and healthy women in the first trimester of pregnancy, and to explore potential associations between them. Methods A total of 26 pregnant women with euthyroid AIT and 30 healthy pregnant women in their first trimester were enrolled. Gut microbiota profiles were analyzed using 16S rDNA gene sequencing, while fecal metabolomic profiling was performed via ultrahigh-performance liquid chromatography-mass spectrometry. Correlations between GM and fecal metabolites were further evaluated. Results Significant diferences in GM composition were observed between euthyroid AIT patients and healthy controls. Metabolomic analysis revealed distinct fecal metabolic signatures in euthyroid AIT patients. Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that diferential metabolites were mainly involved in arachidonic acid metabolism, alpha-linolenic acid metabolism, serotonergic synapses, and bile secretion pathways. Furthermore, a relationship between specific gut microbes and altered fecal metabolites was identified in the euthyroid AIT group. Conclusions Pregnant women with euthyroid AIT in the first trimester exhibit distinct alterations in gut microbiota and fecal metabolic profiles, which may contribute to adverse pregnancy outcomes. Elucidating the correlations between GM and fecal metabolites may provide new insights into potential strategies for preventing and managing complications associated with euthyroid AIT in early pregnancy.