Parallel Assays of Thyrotrophin, Long-Acting Thyroid Stimulator and Exophthalmos-Producing Substance in Some Endocrine Disorders

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Abstract
Bio-assays have been carried out on plasma samples of thyrotrophin (TSH), long-acting thyroid stimulator (LATS) and exophthalmos-producing substance (EPS). The first 2 substances were assayed by discharge of I131 from mouse thyroid glands; EPS was measured by increase in intercorneal distance in fish. The techniques used are reviewed in detail. Plasma TSH levels are reported in 95 bioassays from normal subjects and patients with a variety of endocrine disorders. In 20 cases, all 3 substances were assayed on the same sample. Evidence is presented that EPS and LATS are not the same substance. Emphasis is placed upon the observation that TSH assay by this technique may not be valid in the presence of LATS. The validity of the response ratio is also questioned.