Even in the Era of Congenital Hypothyroidism Screening Mild and Subclinical Sensorineural Hearing Loss Remains a Relatively Common Complication of Severe Congenital Hypothyroidism

Background: Only few studies have focused on neurosensory hearing function of patients with congenital hypothyroidism (CH) identified by CH screening programs and treated early and, therefore, this issue remains still controversial. Objective and hypotheses: The aim of this study was to ascertain whether an early and adequate replacement treatment may be able to prevent sensorineural hearing loss in 32 screened children with CH and no associated risk factors for neuro-otologic alterations. Method: These patients were recruited according to highly selective criteria aiming to preliminarily exclude the negative interference of both treatment variables and other underlying risk factors. All the selected patients underwent, at a median age of 15.4 years, an audiologic investigation. Results: Eight patients (25%) exhibited, at audiometry, a mild sensorineural hearing impairment (between 25 and 40 dB HL), which was bilateral in five cases and unilateral in the remaining three cases. The poorest hearing scores were recorded in the individuals with athyreosis and in those with absence of distal femur bony nucleus at CH diagnosis. The prevalence of hearing impairment was significantly higher in CH patients than in 32 age-matched control subjects with no thyroid problems and no clinical suspect of hearing impairment (25 vs 3.1%; c2Z6.3, P!0.025). Also the prevalence of hearing impaired ears was significantly higher in CH group (20.3 vs 3.1%; c2Z9.1, P!0.0025). Conclusion: i) 25% of CH patients detected by CH screening may show, at a median age of 15.4 years, a mild and subclinical hearing impairment, despite early and adequate replacement treatment; ii) the risk of hearing loss is higher in CH young patients than in age-matched control subjects without thyroid problems; iii) the risk of hearing loss is closely associated with the severity of CH; iv) this risk is particularly relevant in the children with pre-natal onset of hypothyroidism.