Accordingly, the Igf1−/− mouse shows poor growth rates, high mortality, profound sensorineural deafness and late postnatal morphological alterations in the cochlea [16] We have shown previously that the absence of IGF-I causes poor myelination and delayed maturation of auditory neurones that suffer apoptosis during the early postnatal mouse development P5-P20 [17], [18]. Here, IGF1 is linked to deafness.