GENETIC AND ENVIRONMENTAL FACTORS IN CRETINISM: A CLASSIFICATION*

Abstract

Cretinism may arise from a multiplicity of causes. The simplest of these is congenital absence of the thyroid gland. Closely related are cases of aberrantly located fragments of thyroid tissue which represent failure of development of the gland into its normal position. Manifestations of cretinism are not so severe in patients of the latter group. Endemic cretinism arises in association with severe endemic goiter. It is thought to occur when the iodide available to mother and fetus falls below minimal requirements. Genetic and metabolic factors have not been excluded from a role in endemic goiter. Metabolic cretinism occurs when the primary fault is defective synthesis of thyroid hormones. Cases have been attributed to failure of iodide oxidation in the gland, to failure of coupling of hormone precursors into hormones, and to escape and loss of iodotyrosines because of failure of normal deio-dinating processes. Other types doubtless exist.