Hearing loss in congenital hypothalamic hypothyroidism: a wide therapeutic window

In this study, which aims to investigate for the first time auditoty sensitivity in congenital central hypothyroidism (CH), we concluded that: (1) permanent sensorineural hearing loss may be observed not only in congenital primary disorders of thyroid function, as reported hitherto; (2) it may also be found in patients with congenital CH, at least when substitutive treatment is started many years after thyroid failure presentation; (3) the concept of a 'critical therapeutic window' in preventing hearing impairment also holds true for children with congenital CH; (4) the therapeutic window in CH is wider than in primary hypothyroidism; (5) this is probably due to the less severe thyroid impairment in the cases with a central origin of hypothyroidism. These conclusions were suggested by the following data obtained in a cohort of 10 patients with congenital CH who were euthyroid at the time of audiological evaluation thanks to long-standing substitutive therapy: (a) four out of 10 patients exhibited a bilateral sensorineural hearing loss; (b) hearing impaired patients were the oldest of the entire series at diagnosis of hypothyroidism and none of them was aged less than 7 years at the time of the start of replacement therapy; (c) a strong positive relationship was found between age at therapy start and hearing loss.