Protein synthesis in hyperfunctioning human thyroid tissue.

The rate of protein synthesis was examined in vitro in thyroid tissue slices. The material was obtained from euthyroid patients operated on for hyperparathyroidism and from hyperthyroid patients with Graves' disease pre-operatively treated with propranolol alone. The rate of protein synthesis was calculated from the incorporation of [3H]leucine radioactivity in the soluble thyroid proteins (mainly the colloid proteins), the amount of soluble protein per mg tissue and amount of DNA. Based on these figures it was observed that the rate of protein synthesis was 3.2 times higher in the hyperfunctioning thyroid tissue than in the normal tissue. A significant correlation was observed between this activity factor and the serum concentrating of thyroxine. It is concluded that the increased hormone formation in hyperthyroid Graves' disease at least partly depends on an increased rate of protein synthesis in the follicular epithelium. This could be due to stimulation by thyroid immunoglobulins, but other pathogenetic mechanisms may be responsible.