In the duodenum, both YWHAZ (M = 0.0 in CC; 0.5 in CF; 0.3 in CC–CF) and GAPDH (M = 0.0 in CC; 0.5 in CF; 0.3 in CC–CF) were identified as the most stable genes (Table 2). Here, GAPDH is linked to cystic fibrosis.