[Effect of thyroxine on radioactive iodine accumulation in the thyroid glands of hemithyroidectomized rats of different ages].

Experiments were carried out on hemithyroidectomized male rats aged from 2 to 20 months. Thyroxin administration in a dose of 1 microgram per 100 g of body weight on the 5th day of the experiment led to significantly greater suppression of radioiodine accumulation in the lobe of the thyroid gland remaining after the operation in 16--20-month-old rats in comparison with 2--2 1/2-month-old animals. The data obtained confirmed a conclusion drawn earlier on the reduction with ageing of the hypothalamo-hypophysial threshold to the homeostatic thyroxin inhibition.