Insulin-like growth factor I is a possible pathogenic mechanism in nasal polyps.

High concentrations of the trophic peptide insulin-like growth factor I (IGF-I; somatomedin C; SmC) were demonstrated immunocytochemically in all nasal polyps examined, except in areas with necrosis or tissue defects. Most epithelial cells, activated macrophages, and proliferating blood vessels, proved positive, contrasting with the low degree of cellular staining in adjacent normal nasal mucosa. It is proposed that nasal mucosal inflammatory reactions induce local formation and accumulation of IGF-I, which may eventually result in very high IGF-I concentrations in the paranasal sinuses due to the tendency these have to be enclosed, i.e. producing reduced drainage. Assuming that IGF-I constitutes the pathogenic factor, appropriate treatment should be given to reduce the inflammatory reactions and improve drainage.