The gut microbiota of young women had reduced alpha bacterial diversity than that of young men, and furthermore, obese patients with polycystic ovary syndrome (PCOS) have particularly reduced beta diversity and an increased abundance of the Kandleria and Catinebacterium genera, according to a study published in The Journal of Clinical Endocrinology & Metabolism.

To analyze the gut microbiota composition of women with polycystic ovary syndrome, and the influence of obesity, sex, and sex hormones on the findings, the current study enrolled 15 women with PCOS, 16 non-hyperandrogenic control women, and 15 control men. Using body mass index, participants were classified as obese (≥30 kg/m2) or non-obese (<30 kg/m2). Each participant was given a comprehensive clinical, physical, and anthropometric evaluation. Before the evaluation, patients were instructed to follow a 300-g carbohydrate per day diet for the 3 days prior to sampling to avoid false positives in the 75 g oral glucose load test.

Alpha and beta diversity of gut microbiota in the 3 study groups was assessed using Sorensen, Jaccard, Shannon, and Chao 1 estimators. The larger alpha diversity in men was statistically significant regardless of obesity compared with control women, and the Shannon and Chao 1 indexes of all participants showed positive correlations with testosterone concentrations (Shannon: r=0.337, P =.027; Chao 1: r=0.345, P =.023) and the free testosterone/free estradiol ratio Shannon: r=.408, P =.007; Chao 1: r = 0.362, P =.017), and a negative correlation with estradiol (Shannon: r=-0.377, P =.013; Chao 1: r=-0.313, P =.041).

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Regardless of group and sex, an increased abundance of Candidatus Saccharibacteria was found in obese participants compared to non-obese participants (obese=0.06, nonobese=0.02, P =.018). Women with PCOS showed higher relative abundance of Kandleria than men, and Kandleria was absent in control women.  There was an abundance of Catenibacterium and Kandleria in women with PCOS compared with men and women in the control groups.    Total and free testosterone had a positive correlation with an abundance of Raoultella and serum androstendione had a positive correlation with Kandleria.

Study investigators conclude that “the diversity and composition of gut microbiota are influenced by the combined effects of sex, sex hormone concentrations and obesity. Intervention studies designed to unravel the causality of these associations may hopefully permit targeting gut microbiota as putative diagnostic and therapeutic targets for PCOS, obesity and associated metabolic comorbidities.”


Insenser M, Murri M, Del Campo R, Martínez-García MÁ, Fernández-Durán E, Escobar-Morreale HF. Gut microbiota and the polycystic ovary syndrome: influence of sex, sex hormones, and obesity. J Clin Endocrinol Metab. 2018; 103(7):2552-2562.