*5.5.1 Insulin like growth factor 1 (IGF1)*

Animal studies suggest that *Igf1* promotes inner ear neuronal development by supporting neurogenesis, differentiation, and proliferation of neuronal progenitor cells [153, 154]. It has been ubiquitously detected in mouse inner ear, including the spiral ganglion, spiral ligament, stria vascularis, hair cells, and vestibular tissues [155–157]. Numerous variants in *IGF1* have been associated with sensorineural hearing loss in humans and Larson's syndrome; patients who also suffer from early-onset ARHL [158–160].
