Endocrine

Abstract

The thyroid is unique in its ability to accumulate a particular element, iodine, which is not stored to a significant extent by any other tissue. The earliest description of clinical use of a radioisotope of iodine, in a patient with metastatic thyroid carcinoma, was published in 1942 but the availability of radio-isotopes remained restricted until after the cessation of hostilities in 1945. Since that time many in vivo tests have been described. Simultaneously, methods for the assay of circulating thyroid hormones and of pituitary hormones which act on the thyroid have been developed. These assays and their interpretation will not be discussed here but the in vivo techniques described must be viewed in the light of the considerable role played by in vitro measurements in diagnosis and management of thyroid disease.