According to NormFinder analysis, ACTB was consistently identified as the most stable reference gene across all gastrointestinal tissues, exhibiting the lowest stability values in the proventriculus (0.775 in CC; 0.516 in CF; 0.772 in CC–CF), duodenum (1.781 in CC; 1.084 in CF; 0.795 in CC–CF), ileum (0.753 in CC; 0.917 in CF; 0.811 in CC–CF), and jejunum (0.931 in CC; 0.931 in CF; 0.888 in CC–CF) (Table 3). The gene discussed is ACTB; the disease is cystic fibrosis.