[Effect of the ingestion of soybean fractions, raw or autoclaved, on the rat thyroid].

Feeding rats for 16 days a water soluble fraction from raw soy flour caused a 40% enlargement of thyroid weight, a similar decrease of 131I uptake and an increase of tri-iodo-thyronine-binding capacity of rat serum. This effect was heat labile. The same fraction autoclaved was able to reduce radioactive iodine uptake and to decrease T3-binding capacity. In longer assays (29 days) this same fraction produced a 30% increase of 131I uptake and altered thyroid hormones increasing T3 and T4 synthesis. An increase of MIT/DIT and a decrease of T3/T4 ratios was also observed by the authors.