Based on studies indicating that IGF-1 administration in the auditory system improves hearing in individuals with hearing impairment (Nakagawa et al., 2014), and that IGF-1 stimulates collagen biosynthesis and helps to prevent skin aging (Takasao et al., 2012; Blackstock et al., 2014), IGF-1 is expected to directly affect the olfactory system or have indirect effects by stimulating the synthesis of collagen type 1. This evidence concerns the gene IGF1 and Hearing impairment.