1962 Volume 38 Issue 9 Pages 942-953,878
1) Fecal excretion of thyroxine increased greatly when young rats were fed powdered cellulose, barium sulfate or clay, added to the basal diet and then injected with I131-thyroxine.
2) A significant decrease in the thyroidal uptake of I131 occurred in 4 days. After 2 months on these diets, marked decreases in the weights of the thyroid glands and in I131 uptake, as well as degenerative atrophy of the thyroid glands were noted in the histologic picture. No changes were noted in other endocrine glands.
3) The inhibitory effects on the thyroid of the cellulose diet increased in a cold environment, and decreased in a warm environment. No inhibitory effect was noted in adult rats. The inhibitory effects appear to be based on thyroid hormone deficiency.
4) The inhibitory effects on the thyroid could not be observed when PTU or iodide was added to the cellulose diet. The inhibitory effects on the thyroid were noted when cellulose was added to a low iodine diet.
5) The formation of goiter occurred when excess iodide was added to the cellulose diet in a warm environment.
6) No significant difference in the rate of body weight increase was observed between the cellulose and control groups during the first 2 months, but after.2 months a decrease in the rate of body weight was noted in the cellulose groups as compared to the control groups.
7) After 2 months of cellulose diet an increase in thyroxine degradation rate was determined from the results of I131 excretion rate in urine and I131 distribution in the body after I131-thyroxine administration.
8) A decrease in the PBI and an increase in the T3-erythrocyte uptake was noted after 2 months of cellulose diet ; after 6 months we noted a decrease in both.
9) The classic feed-back theory states that the activity of the centers regulating thyroidal function is controlled by the level of circulating thyroid hormone. This theory makes it difficult to explain our data and so we have theorized that the activity of the centers regulating thyroidal function is controlled by the degradation rate of thyroid hormone in peripheral tissues.
