Click-evoked otoacoustic emissions recorded from untreated congenital hypothyroid (CH) newborns

Thyroid hormone plays an important role in hearing development. Both a genetic or non-genetic hypothyroidism is often associated with congenital hearing loss. The exact incidence of hearing impairment in untreated congenital hypothyroid (CH) patients is unknown. This paper will present the results of measuring of the transient-evoked otoacoustic emissions (TEOAE) in a population of 29 newborns, who tested positive on a screening test for hypothyroidism (CH group) and in 68 well babies (control group) randomly chosen from all the newborns, classified as PASS, included in the Hearing Screening Program of the San Raffaele Hospital in Milan. TEOAE were recorded in all newborns within 1 month after birth and before beginning L-thyroxine treatment with conventional commercial instrumentation. Both temporal and time-frequency analyses of the emitted responses were conducted by means of a wavelet transform. The comparison of the characteristics of the temporal and frequency content of the responses of the two groups (CH and control) showed no statistically significant difference. No correlation was found between outer hair cell dysfunction and hypothyroidism.