The inclusion of arachidoside and anacardioside, the pigments isolated from the outer skin-covering of groundnuts and cashewnuts respectively, in the diet of rats, at a level of 20 mg per rat per day for 7 weeks results in goitre. Incorporation of potassium iodide in the diet counteracts partially the goitrogenic action of the anthocyanins. Results of studies on the distribution of radioactive iodine in the thyroid glands of the rats suggest that the pigments inhibit the organic binding of radioactive iodine. An anthocyanin pigment and a catechin have been isolated from almonds and areca nuts respectively. In vitro experiments employing the tissue slice as well as homogenate technique reveal that all of the above 4 test compounds interfere with the organic binding of radioactive iodine. The test compounds form stable iododerivatives which, however, do not possess any significant inhibitory effect on the organic binding of radioactive iodine. The implications of the results are discussed
