Table 3. Association between estrogen and testosterone and the bacterial composition and diversity.

Summary of findings from the three studies that investigated the association between both estrogen and testosterone and the bacterial composition and/or diversity. Two of these studies investigate the effects of testosterone and estrogen on both the bacterial composition and diversity, whilst one study only investigated their effects on bacterial composition.

N/A: not applicable; PCOS: polycystic ovary syndrome.

Study	Estrogen		Testosterone
	Bacterial Composition	Bacterial Diversity	Bacterial Composition	Bacterial Diversity
Insenser et al.(30)	↓ Paraprevotella genus (healthy men, healthy women and women with PCOS were considered as a whole)	↓ Alpha diversity (healthy men, healthy women and women with PCOS were considered as a whole)	↑ Raoultella and Paraprevotella genera (healthy men, healthy women and women with PCOS were considered as a whole)	↑ Alpha diversity (healthy men, healthy women and women with PCOS were considered as a whole)
Shin et al.(25)	↓ Slackia and Butyricimonas genera (All associations seen in healthy women)	↑ Alpha diversity in healthy women	↑ Acinetobacter, Dorea, Ruminococcus and Megammonas genera in healthy men	↑ Alpha diversity in healthy men
Zhou et al.(28)	↑ Subdoligranulum, Collinsella, Sutterella and Agathobacter genera (obese women with PCOS) ↓ Escherichia-Shigella and Ruminococcus_gna vus_group genera (obese women with PCOS) ↑ Parasutt`erella and Dialister genera (non-obese women with PCOS)	N/A	↑ Ruminococcus_2 and Collinsella genera (obese women with PCOS) ↑ Prevotella_2 and Megasphaera (non-obese women with PCOS)	N/A

^*↑ denotes a positive association between the sex hormone and the outcome of interest.

^*↓ denotes a negative/inverse association between the sex hormone and the outcome of interest.

^*↔ denotes a lack of association found between the sex hormone and the outcome of interest