TNF and isolated hemihyperplasia: TNF‐α, which is known to induce airway inflammation and excessive mucus secretion by activating various inflammatory cells and releasing proinflammatory cytokines including IL‐6 and IL‐8, was also not significantly different in the IHP group, which may explain the lack of a significant increase in airway mucus secretion observed in the IHP group compared to the RA and IH groups.