Hearing in congenital hypothyroidism.

The hearing profile of children with congenital hypothyroidism was studied in 45 patients with thyroid gland agenesis, hypogenesis or dyshormogenesis, during adequate substitution therapy. Preliminary, secretory otitis media was found in 6 patients under the age of 6 years; in these children, hearing assessment was performed after cure of the middle ear effusion. Hearing threshold was measured either by conventional pure-tone audiometry or conditioned orientation reflex audiometry according to the patient's age (above and below 4 years). In 36 patients (80%) the auditory thresholds were normal; in the remaining 9 patients (20%) a sensorineural hearing loss of different degree was detected; in 5 cases (11%) the deafness was important and required auditory rehabilitation, with the use of a hearing aid in 4 of them. No relation could be found between hearing acuity and bone age at diagnosis of hypothyroidism or aetiology of thyroid dysfunction. It is concluded that in about one tenth of the children with congenital hypothyroidism a substantial deafness persists. The sensorineural nature of the hearing loss is in agreement with reported histological findings in congenital hypothyroid animals, where an immature development of the organ of Corti including hair cells and tectorial membrane has been observed.