241Am-induced thyroid lesions in the beagle.

One of the features of 241Am metabolism in the beagle dog is a relatively high selective deposition in the thyroid glands, equal to approximately 0.06% of the injected dosage per gram. Retention is prolonged and principally in the interstitial connective tissue. The resulting average dose to the thyroid glands is about 1.42 and 0.76 times that delivered to the skeleton and the liver, respectively. This thyroid dose is much higher than has been reported in people. Although significant morphological changes and reductions in serum thyroxine occurred in this experiment, a significant increase in thyroid neoplasia was not observed.