Approximately eighteen centuries ago Galen described the thyroid gland. One century ago Cooper experimentally removed the gland from a dog. Sixty years ago myxedema was described, and forty years ago thyroid juice was injected subcutaneously as a cure. Twenty years ago Kendall isolated and synthesized thyroxine. Thirty years ago a German compiled a tome listing the books, monographs and papers on the subject of cretinism—a total of 2,468 titles. Since then the literature has expanded enormously.
Among all the reports of investigations there is none of a detailed objective study of the effect of thyroxine on early mental growth. These effects are truly remarkable. The aim of this paper is to describe their nature, to show the relationships between psychologic and physical factors and to indicate the diagnostic significance of the behavior changes produced by thyroid therapy.
It is commonly asserted that the early diagnosis and treatment of cretinism are