Iodine Components of the Blood. Circulating Thyroglobulin in Normal Persons and in Persons With Thyroid Disease

Abstract

It is now well established that the amount of iodine circulating in the blood is roughly an index of thyroid activity. Iodine values below 5 gamma per cent are usually found in myxedema, and values over 10 gamma per cent are suggestive of hyperthyroidism. A portion of the blood iodine is inorganic and presumably inert in a hormonal sense; the remainder is organic and probably represents the circulating hormone or its components. Very little is known of the nature of this organic iodine. In the course of experimfients on the production of antibodies to human thyroglobulin, it seemed that antiserum potent with respect to thyroglobulin antibodies might be used to detect thyroglobulin in human serum by appropriate immunologic reactions. METHODThe technique used to obtain antithyroglobulin serum is similar to that of Hektoen and Schulhof (1), Rosen and Marine (2), and Schulhof (3). Thyroglobulin was prepared from human thyroid glands which had been removed at operation and made relatively free from serum.1 It was kept in suspension at its isoelectric point. The protein content was usually 1.5 to 2.0 per cent, and the iodine about 5 to 6 mgm. per cent. This material was injected into rabbits intraperitoneally, intravenously, or into subcutaneous nodules according to the method described by Dienes (4). The injections were given for 2 to 3 days in succession, with rest periods of 4 to 6 days. The intraperitoneal injection contained about 75 to 150 mgm. of thyroglobulin, the intravenous injection 15 to 20 mgm. and the intranodular injection 1 to 3 mgm. for each nodule. After a period of 4 to 8 weeks, the serum of such animals usually contained sufficient antibodies to be of value in testing for very small amounts of thyroglobulin. In some instances, animals were injected for several months in succession in order to increase their antibody titer. The rabbit antiserum contained not only antibodies for human thyroglobulin but also small amounts of antibodies for human serum protein. before using such serum in immunologic tests it was necessary to absorb the antibodies against human serum. This was done by mixing the antiserum with human serum in the proportion of 1 to 0.25, incubating the mixture overnight, and centrifuging the small precipitate formed. A similar absorption technique was used by Stokinger and Heidelberger (5).The presence of antibodies was determined by the ring precipitin test, using the undiluted rabbit serum against dilutions of thyroglobulin or human serum. Thyroglobulin was first dissolved in dilute alkali at a pH of 8.0 to 9.0 until it was almost clear and the insoluble portion removed by centrifugation. Normal saline used in making dilutions was also adjusted to the same pH. Otherwise, at the usual pH of normal saline there would be precipitation of thyroglobulin.2 The antiserum was introduced at the bottom of small tubes and the dilutions of thyroglobulin or human serum were layered on top. The results were read after 1 to 2 hours at room temperature.In attempting to evaluate the potency of the anti...

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