ObjectiveTo analyze the expressions of IL1β, endotoxin in secretory otitis media (SOM) after radiotherapy for nasopharyngeal carcinoma (NPC), and to explore the relationship between its pathogenesis and eustachian tube dysfunction.MethodsAerobe and facultative anaerobes culturings and drug sensitive tests were conducted in the collected middle ear effusion. Meanwhile, enzymelinked immunosorbent assay and kinetic turbidimetric limulus test were applied to measure the expressions of TNFα, IL1β and endotoxin in middle ear effusion and serum.Results①Bacterial culture showed positive results in one case of the common group with acinetobacter Baumannii, two cases of the radiotherapy group with staphylococcus aureus. ②Endotoxin detection revealed that the values of endotoxin expression in middle ear effusion were higher than those in the serum in both the common and radiotherapy groups (both P<0.05), and the value in middle ear effusion of the radiotherapy group was higher than that of the common group (P<0.05). ③The expression values of IL1β, TNFαin middle ear effusion were higher than those in the serum in both the common and radiotherapy groups (both P<0.05), but their differences in middle ear effusion between the two groups were statistical insignificant(both P<0.05). ④The expression values of IL1β in the radiotherapy group showed significant differences among subgroups with complete obstruction, incomplete obstruction and complete shutting of eustachian tube (all P<0.05).ConclusionThe characteristics of SOM after radiotherapy include low positive rate of bacterial culture, as well as high expression rates of IL1β, endotoxin and TNFα in middle ear effusion. Endotoxin may be an important factor among multiple factors causing a protracted disease process. The degree of eustachian tube obstacle is closely related to the expression value of IL1β in the middle ear effusion of SOM after radiotherapy for NPC.