Four studies (1 adult and 3 pediatric) comprising a total of 191 NAFLD patients (135 paediatric and 56 adult) and 162 HC (142 pediatric and 20 adult) were included in the quantitative synthesis of the mean serum zonulin levels in NAFLD patients and HC (Figure 1B). This evidence concerns the gene HP and metabolic dysfunction-associated steatotic liver disease.