Daidzein-metabolizing phenotypes in relation to serum hormones and sex hormone binding globulin, and urinary estrogen metabolites in premenopausal women in the United States.

OBJECTIVE: Blood and urine concentrations of hormones are implicated in the etiology of some cancers. Small studies have assessed relationships between production of the daidzein metabolites equol and O-desmethylangolensin (ODMA) and hormones, but findings are unclear. We evaluated relationships between daidzein-metabolizing phenotypes and follicular phase concentrations of estrogens, androgens, sex hormone binding globulin (SHBG), and urinary estrogen metabolites in premenopausal women.
METHODS: Two-hundred women collected a first-void urine sample after a 3-day soy challenge, and 191 and 193 provided fasting blood and spot urine samples, respectively, during days 5-9 of their menstrual cycle. Soy challenge urines were analyzed for isoflavones; serum was analyzed for estrogens, androgens, and SHBG; spot urines were analyzed for 2-hydroxyestrone and 16alpha-hydroxyestrone. Data were log-transformed and multiple regression analyses were conducted to assess relationships between daidzein-metabolizing phenotypes and hormones and SHBG. Data from 187 and 189 women were included in analyses of serum and urine hormones, respectively.
RESULTS: 55 (27.5%) and 182 (91%) of the 200 women who provided a soy challenge urine sample were equol- and ODMA-producers (>87.5 ng/ml urine), respectively. In unadjusted analyses, equol-producers (n = 52) had lower free testosterone than equol non-producers (n = 137, p = 0.02). In adjusted analyses, there were no differences between producers and non-producers of either daidzein metabolite.
CONCLUSIONS: In the absence of a soy intervention, we found no difference in serum or urine hormone concentrations between producers and non-producers of equol or ODMA.