Thyroid Destruction by I 131 , and Replacement Therapy

Abstract

26 New Hampshire chicks weighing 40-66 g. were injd. intra-perit. with carrier-free I131; dosage ranged from 1 to 9.2 m.c./ 100g. of body wt. Animals were sacrificed after periods ranging from 5 to 140 days after injn., and histological studies of the thyroid tissue or thyroid region were prepd. to evaluate the degree of thyroid destruction caused by the I131; such destruction is designated as radio-thyroidecresis. The degree of destruction is roughly proportional to the dosage, with dosages of about 6 m.c./100g. or greater producing complete destruction. Thyroid-ecrecticized birds showed marked reduction in growth, and survived for only short periods; similarly treated birds receiving daily injns. of 3.8 or 5.7[mu]g. of thyroxin/100 g. of body wt. showed normal growth and egg production.