An experimental approach to the understanding and treatment of hereditary syndromes with congenital deafness and hypothyroidism.

Hereditary syndromes with congenital deafness and hypothyroidism have been reported from many countries. The large majority of them are believed to form a single genetic entity, known as Pendred's syndrome, and inherited as a recessive trait. The anatomical basis of deafness is not known. It is generally believed that deafness and hypothyroidism are not causally related, but are independent effects of the gene. The object of this investigation was to test this view by means of induced hypothyroidism. Mice from the inbred strain C57BL/Gr were given 0·1% propylthiouracil (PTU) in drinking water, and their offspring were examined. They were found to be practically deaf, and to have serious abnormalities in the inner ear. Addition of thyroxine to the drinking water containing PTU resulted in normal hearing and a normal inner ear, showing that the abnormalities were not caused by PTU as such, but were the consequence of its inhibitory effect on thyroid function. It is, therefore, highly probable that in Pendred's syndrome and other similar conditions the loss of hearing is secondary to hypothyroidism during fetal life. Suggestions are put forward for mitigating the expressions of these syndromes by treatment with thyroxine during certain stages of development.