Graphical Abstract.

Jiang et al. report that the abundance of Eggerthella significantly increased in fecal samples of patients with premature ovarian insufficiency. Moreover, circulating metabolites and TGF-β1 levels were elevated in these patients. These alterations were all reversed by HRT. The abundance of Eggerthella was positively correlated with the increased circulating metabolites, which were, in turn, positively correlated with the serum levels of TGF-β1, a profibrotic factor. * indicates positive correlations, *P<0.05.