A retrospective study of audiological function in a group of congenital hypothyroid patients.
A retrospective survey has been carried out on audiological function in 46 congenital hypothyroid cases; mental and physical development were also assessed, as well as the adequacy of substitutive therapy. Using traditional audiometry it was found that 50% of the congenital hypothyroid patients were hypocusic. Severe and profound hearing loss (5 cases) was found in the group of hypothyroid patients with dyshormonogenesis, whereas only one-third of patients with thyroid agenesis presented a mild or moderate hearing loss not related to the time of diagnosis and treatment. The hearing loss was twice as frequent in the patients with clinical hypothyroidism. Using electrophysiological techniques, the early or slow potentials were comparable between hypocusic or normocusic patients; however a longer latency of the slow vertex responses was observed in the hypothyroid group as compared to the normal population. The mean estimated I.Q. was about 2 standard deviations below the average; however 30% of subjects had normal or above normal intellectual level, this percentage rises to 55% if only patients below 16 years are considered. The height was significantly shorter only in the late treated patients (1 year). No correlations were found among audiological and psychological variables, nor between these variables and height. All patients were on desiccated thyroid, but therapy was inadequate in 26% of cases and subclinical hypothyroidism was found in 33% of cases.