Serum steroid hormones, sex hormone-binding globulin concentrations, and urinary hydroxylated estrogen metabolites in post-menopausal women in relation to daidzein-metabolizing phenotypes

Equol and O-desmethylangolensin (O-DMA) are products of bacterial metabolism of daidzein, an isoflavone in soybeans; thus, the presence or absence of equol and/or O-DMA in urine is a marker of particular intestinal bacteria profiles. Plasma hormone concentrations may be lower in pre-menopausal women who harbor the bacteria capable of producing equol (equol producers) compared to women who do not (equol non-producers). We evaluated concentrations of serum hormones, sex hormone-binding globulin (SHBG), and urinary 2-hydroxyestrone (2-OH E₁) and 16-hydroxyestrone (16-OH E₁) in relation to equol-producer and O-DMA-producer phenotypes in 89 post-menopausal women. Follicle stimulating hormone (FSH) was 23% greater in O-DMA-producers compared to non-producers (P=0.04). No significant differences in serum estrogens, androgens, metabolic hormones, or SHBG were observed in relation to either daidzein-metabolizing phenotype. Compared with non-producers within each phenotype, age-adjusted 2-OH E₁:16-OH E₁ was 27% greater (P=0.06) in equol-producers and 9% greater (P>0.10) in O-DMA-producers, and 2-OH E₁ concentrations were 24% greater in equol producers (P=0.07) and 42% greater in O-DMA producers (P=0.02). No significant differences in 16-OH E₁ were observed in relation to either phenotype. These results suggest that interindividual variability in intestinal bacteria may be related to differences in products of hormone metabolism in post-menopausal women.