Hypothyroidism due to enzyme defects.

Defects in thyroid hormone production, transport and utilization are classified. Particular attention is given to inherited intrathyroidal defects in hormone synthesis which impair thyroid function and lead to goitre formation and hypothyroidism. Anomalies in biosynthesis may also result from disease or drugs. Reference is made to the derangement of iodine metabolism that results from iodine deficiency and from insufficient TSH. Illustrative clinical problems with regard to transport and utilization are quoted, and it is inferred that they lie in rather neglected areas. Throughout an attempt has been made to show how the clinical problems that are encountered in practice may, by the techniques of investigation available to us, be related to the theoretical list of defects that are included in the classification.