Different studies have shown that IGF2 mRNA expression was 10–20-fold higher and IGF2 protein expression 8–80-fold greater in ACC compared to normal adrenal glands or adrenocortical adenomas (ACA), speculating that different IGF2 concentrations could be responsible for different biological behaviors of ACC [17,18,19,20,21,22]. This evidence concerns the gene IGF2 and adrenal cortex adenoma.