Urinary Isoflavones Levels in Relation to Serum Thyroid Hormone Concentrations in Female and Male Adults in the U.S. General Population

ABSTRACT

Isoflavones are phytoestrogens found in plant-based foods and nutritional supplements. Experimental studies show a positive association between isoflavones and hypothyroidism, but epidemiological findings are conflicting. We used multivariable linear regression to examine the association between urinary isoflavone concentrations and serum thyroid hormone concentrations in the National Health and Nutrition Examination Survey (2007–2010). In this study, we found that Daidzein and O-DMA associations with free T4 were stronger among women: a 10-fold increase in daidzein was associated with a 3.2% (95% CI: 1.9%, 4.5%) increase in women and a 0.6% (95% CI: −1.7%, 0.6%) decrease in men and a 10-fold increase in O-DMA was related to a 2.0% (95% CI: 1.1%, 2.9%) increase in women and a 0.3% (95% CI: −1.2%, 0.5%) decrease in men. In this study, selected urinary isoflavone concentrations were associated with serum thyroid hormone concentration in a sex-dependent fashion.

KEYWORDS:

• Isoflavone
• phytoestrogen
• thyroid

Acknowledgments

The authors would like to acknowledge the support of the Boston University school of Public Health Pilot Funding Program.

Disclosure of interests

The authors report no conflict of interest.

Supplementary material

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