The inherited errors of the thyroid system

Some of the inborn errors of the thyroid system are reconsidered after reflection on old studies and in the light of some new information. The peroxidase defect is seen as at least four distinct entities with deficient iodination of tyrosyl residues of thyroglobulin as the final common expression. Three of these may be allelic for thyroid peroxidase, but the fourth, the Pendred syndrome, is almost surely not.

Present information does not seem to allow for three separate errors which in the past have been designated as ‘coupling defect’, ‘thyroglobulin synthesis defect’, and the syndrome of ‘abnormal plasma iodoprotein’.

Patients with the syndrome of thyroid hormone unresponsiveness differ in different kindreds. The disorders may or may not be allelic. Recent findings on the molecular mechanism of thyroid hormone action promise an early understanding of the nature of this disorder, perhaps as an error in the protein of nuclear chromatin which binds the hormone. Other inborn errors of the thyroid are briefly mentioned.