[Chloroderivatives of phenoxyacetic acid as antagonists of thyroid hormones]

A 24-hour stay of the Rana temporaria tadpoles in solutions of the sodium and diethylamine salts of 2,4-dichlorophenoxyacitic acid (with 1 and 2 mg/l, respectively) significantly inhibits their metamorphosis. An addition of these salts to a solution containing thyroidin in a concentration of 1--5 mg/l hinders the action of hormone stimulating metamorphosis. The effect of the sodium salt of 2,4-dichlorophenoxyacetic acid prevents the destruction of some tadpoles by toxic concentrations of thyroidin. The above data justify referring the chloroderivatives of the phenoxyacetic acid to antagonists of the thyroid hormones.