Introduction: Thyroxine plays a key role in the development of the structures of the ear, the auditory pathway and in myelination of the central nervous system. The association between congenital hypothyroidism (CH) and neurodevelopmental outcome is clearly established. However, there is a lack of data about the prevalence and severity of hearing loss in the CH population.
Methods: Between 1/1/12 and 31/12/13, 187 children were diagnosed with CH and treated with levothyroxine after referral through the North Thames Newborn Screening programme at Great Ormond Street Hospital. Biochemical, sociodemographic, and technetium scan data were collected. All infants were referred for audiological assessment at 2 and 8 months. Auditory brainstem response (ABR) testing at 2 months and visual reinforcement audiometry (VRA) at 8 months, along with otoaucoustic emissions (OAE) testing was used to ascertain hearing outcomes.
Results: 121/187 (64.7%) patients attended the 2-month hearing assessment, and 87/187 (46.5%) completed the 8-month assessment. Of those tested, results revealed a prevalence of mild hypothyroid-related hearing loss of 30% at 2 months and 18% at 8 months in this CH cohort. These are both statistically significant at the 5% level, when compared with the prevalence of 0.24% in the general paediatric population. Both TSH and T4 levels were shown to have a strong positive relationship with hearing outcomes, P=0.036 and P=0.001 respectively. Gender (P=0.639), ethnicity (P=0.675), and thyroxine requirements (P=0.806) were not shown to have a statistically significant effect on hearing outcomes. ABR latencies at 2 months were shown to be slightly delayed at all intensities in agenesis patients, suggesting that there is delayed myelination in this group. 3/187 infants in this study failed the newborn hearing screening test.
Discussion/conclusion: Infants with congenital hypothyroidism experience greater hearing loss than the general paediatric population. Only 3/187 infants in this study failed the newborn hearing screening test, therefore it was concluded that the programme is not sufficient at identifying hearing loss in infants with congenital hypothyroidism. We recommend that auditory referral should be considered for all infants diagnosed with congenital hypothyroidism.
25 - 27 Nov 2015
British Society for Paediatric Endocrinology and Diabetes