Effects of the Injected Human Serum Containing Long-Acting Thyroid Stimulator on the Thyroidal Function and Structure

Abstract

The long-acting thyroid stimulator (L.A.T.S.) was distinguished from the thyrotropin by its prolonged action to release I¹³¹ from the thyroid in an assay for TSH. However, it is still questionable whether or not L.A.T.S. has really long-acting activity to stimulate the thyroid function. In this study the following experiments were carried out to clarify this problem. Hyperthyroid serum containing a high concentration of L.A.T.S. was injected intravenously to the mice every day for nine days and the thyroidal function was examined on the fourth day after the final injection. As controls, thyrotropin, normal human serum or saline solution were injected to mice in the same manner. In the first experiment thyroxine was not given to the mice, but in the second experiment thyroxine was injected subcutaneously six times every other day from the first injection of L.A.T.S. and control materials to supress the secretion of thyrotropin. The activity of TSH was measured by the Noguchi modification of McKenzie's method and the thyroidal function was examined by I¹³¹ uptake rate, conversion ratio and PBI¹³¹ (% dose per liter) at 24 hours after injection of I¹³¹. The metabolic course of iodine in the thyroid gland was observed by paper chromatography, and the histologicol changes studied by autopy.
The results are shown in Table 1, 2 and Fig. 1. The thyroidal function of mice receiving the injection of L.A.T.S. was more strongly activated than that of control animals when the feed-back mechanism of thyroid-pituitary was supressed by thyroxine injection. However, in the first experiment (in which mice did not receive thyroxine) there was not a significant difference in the thyroidal function between the mice which were injected with L.A.T.S. or control meterials because the level of TSH in the circulating blood was controlled by the endgenous thyrotropin secretion even though L.A.T.S. has prolonged activity. The histologic structure of the thyroid in mice which receivid L.A.T.S. and thyroxine was significantly different from that of control animals : acinal cell height increased and its plasma was clear just as commonly observed at the part of papillary proliferation of acinal cells in hyperthyroidism. However, when thyroxine was not given these specific findings were not observed.