Genistein aglycone does not affect thyroid function: results from a three-year, randomized, double-blind,...

Area of Science:

• Endocrinology
• Nutritional Science
• Women's Health

Background:

• Genistein aglycone is recognized for its positive effects on postmenopausal symptoms.
• However, concerns regarding its long-term safety, particularly its impact on thyroid gland function, persist.

Purpose of the Study:

• To investigate the long-term safety of genistein aglycone supplementation on thyroid function in postmenopausal women.
• To assess the effects of genistein aglycone on thyroid hormones, autoantibodies, and receptor gene expression.

Main Methods:

• A 3-year randomized, double-blind, placebo-controlled trial involving 389 osteopenic, postmenopausal women.
• A subcohort received 54 mg of genistein aglycone daily or placebo, alongside calcium and vitamin D3.
• Assessed serum thyroid hormones (TSH, free T3, free T4), autoantibodies, and gene expression of thyroid hormone receptors (THRalpha, THRbeta) and retinoid receptors (RARalpha, RARgamma, RXRalpha).

Main Results:

• Genistein aglycone administration for 3 years did not alter serum thyroid hormone levels or thyroid autoantibodies.
• No significant differences in the mRNA expression of THRalpha, THRbeta, RARalpha, RARgamma, or RXRalpha were observed between the genistein and placebo groups.
• The study found no adverse effects on thyroid function markers.

Conclusions:

• Genistein aglycone intake at a dose of 54 mg/day does not appear to increase the risk of clinical or subclinical hypothyroidism.
• These findings support the long-term safety of genistein aglycone for thyroid health in postmenopausal women.