Endocrine Review: THE CLINICAL SIGNIFICANCE OF THE BLOOD IODINE: A REVIEW*

THE past decade is replete with discoveries which have added to our understanding of the nature of thyroid disease, as well as to our concepts of the metabolism of iodine, the element so intimately involved in the cellular physiology of the thyroid gland. A number of these have developed directly from experiments concerned with determinations of the blood iodine. Until recently blood iodine determinations, because of tedious, complicated, and time-consuming methods, have been restricted to the research laboratory. However, simplified methods which will enable any good clinical laboratory easily to determine blood iodine levels have become available. As a consequence the blood iodine is now assuming a significant position in the armamentarium of the clinician, to be used in the diagnosis of thyroid diseases as well as to aid in differentiating disorders of the thyroid gland from the many pathologic conditions which may simulate them. It was a fortunate empiricism which prompted the ancients to use burnt sponge and seaweed in the treatment of goiter. The presence of iodine in sponges was demonstrated soon after the element had been discovered by Courtois (1) in 1811 and publicly announced by Clement (2) in 1813. This related iodine at once with the study of goiter. Subsequent biochemical investigations concerning the thyroid gland have centered largely around that element.