The Thyroid Hormone-Plasma Protein Complex in Man. Ii. A Newin Vitromethod for Study of “Uptake” of Labelled Hormonal Components by Human Erythrocytes*†

SIGNIFICANT advances in elucidation of various aspects of normal and abnormal thyroid function have resulted from the use of I131, chromatography, and chemical quantitation of serum protein-bound iodine levels. The major emphasis in earlier studies was on the thyroid gland itself—its uptake and organification of iodine, and the release into the circulation of a thyroxine-like moiety. In recent studies the focus has shifted somewhat from the gland to such problems as 1) the qualitative nature of the hormone(s)-plasma protein complex, 2) the fate of this complex following its elaboration, and 3) the mechanism of its action on the peripheral tissues. Investigations of these questions have indicated the need for consideration of multiple parameters of thyroid function as an important approach to some of the remaining unsolved problems. The purpose of this report is 1) to present a new method for study of the in vitro incorporation of thyroid hormonal components by the human erythrocytc, 2) to summarize results of its use in a variety of clinical conditions, and 3) to evaluate its possible contribution, as another parameter, to our knowledge of thyroid function.