NOS2 and nasal cavity polyp: In our study, PDE5, eNOS and iNOS levels were measured by ELISA in tissues obtained from patients with nasal polyps who underwent endoscopic sinus surgery and rhinoplasty for anatomical variations.We found that PDE5 levels decreased statistically significantly in the nasal polyp group compared with the control group, and eNOS and iNOS levels increased in parallel with decreased PDE5 levels.