Experimental Study on the Nature of Long-Acting Thyroid Stimulator which is Present in Hyperthyroid Serum

Abstract

The studies to clarify the difference between thyrotropin and long-acting thyroid stimulator (LATS), which is present in serum of thyrotoxic patients, were centered on the stability, the dose response relationship, and the mixing test of thyrotropin and serum containing LATS. The results are summerized as follows : 1) The dose response relationship for hyperthyroid serum containing LATS and for thyrotropin (USP, thyrotropin Reference Standard, 0.1mu.-0.8mu.) diluted with normal serum was studied. The dose response line of LATS differed from that of thyrotropin at high doses. With thyrotropin, the dose response line became horizontal when the responses reached 800-900. However, the LATS 12-hour response line was still rising steeply even when the response was between 1000-1500 (Fig.1).2) Stability of serum containing LATS was examined for the storage (102 days, at 4°C), heat and pH under various conditions. However, there was no significant difference between LATS and thyrotropin in serum (Fig.2, Table 1).3) When thyrotropin was mixed with hyperthyroid serum containing LATS, two types of response were encoutered : in the first type the response, reported by Adams and Munro, seemed to closely approximate the arithmetical sums of the responses to the serum which contained LATS and thyrotropin given separately (Fig.3).In the second type, the 12-hour response of the mixed serum increased much more than that of hyperthyroid serum which was given independently (Fig.4).These results suggest that the activity of thyrotropin in the mixture continued for 12 hours by the combination of thyrotropin with some factor in hyperthyroid serum.