Soya does not affect thyroid function!

A new 3 year study on soya & thyroid function appears to show no affect on the thyroid function. Like any study this doesn't prove there is no link, but it does seem to imply that we understand less about how some of these chemicals work in the real world than we think.
Here's the abstract:

Quote :

http://www.ncbi.nlm.nih.gov/pubmed/20357174

J Clin Endocrinol Metab. 2010 Jun;95(6):3067-72. Epub 2010 Mar 31.
Genistein aglycone does not affect thyroid function: results from a three-year, randomized, double-blind, placebo-controlled trial.

Bitto A, Polito F, Atteritano M, Altavilla D, Mazzaferro S, Marini H, Adamo EB, D'Anna R, Granese R, Corrado F, Russo S, Minutoli L, Squadrito F.

Department of Clinical and Experimental Medicine and Pharmacology, Section of Pharmacology, University of Messina, 98125 Messina, Italy.
Abstract

CONTEXT AND OBJECTIVE: Genistein aglycone positively affects postmenopausal symptoms. However, questions about its long-term safety on the thyroid gland still remain.

DESIGN: The parent study was a randomized, double-blind, placebo-controlled trial involving 389 osteopenic, postmenopausal women for 24 months. A subcohort (138 patients) continued therapy for an additional year.

SETTING: Patients received ambulatory care.

PATIENTS AND INTERVENTIONS: Participants received 54 mg of genistein aglycone daily (n = 71) or placebo (n = 67), plus calcium and vitamin D(3) at therapeutic doses. Circulating thyroid hormones (TSH, free T(3), free T(4)) and autoantibodies (thyroid peroxidase, thyroglobulin, and thyroid microsomal antigen) were assessed in 40 genistein and 37 placebo subjects who completed 3 yr. Thyroid hormone receptor (THRalpha and THRbeta) and retinoid receptor (RARalpha, RARgamma, and RXRalpha) expression from peripheral blood monocytes was also evaluated at baseline, 12, 24, and 36 months in all 3-yr completers.

RESULTS: Genistein administration over 3 yr did not affect serum thyroid hormones or autoantibodies. In addition, there were no differences in THRalpha, THRbeta, RARalpha, RARgamma, or RXRalpha mRNA expression between groups.

CONCLUSION: These data suggest that genistein aglycone intake does not significantly increase the risk of clinical or subclinical hypothyroidism at the dose of 54 mg/d.