Insulinlike growth factor I immunoreactivity in nasal polyps.

Nasal polyps from 15 patients were all found to express increased insulinlike growth factor I immunoreactivity. A hypothesis for the formation of nasal polyps is described: macrophages, seen in allergic and infectious reactions, produce and release growth factors, tentatively including insulinlike growth factor I. In enclosed paranasal sinuses this results in an accumulation of insulinlike growth factor I stimulating the growth of both epithelium and blood vessels in the sinuses. The mucosa increasingly bulges out through the ostium after having filled out the sinusity. Continuing growth stimulation is supplied by the inflammatory reaction, endothelial cells in the polyp, and activated macrophages inside or outside the polyp.