The activity of SONIC HEDGEHOG (SHH) pathway, crucial during embryogenesis and organ development, differs among PA subtypes, being downregulated in NFPAs as compared to normal pituitary tissues, while GLI1, one of the transcriptional effectors that mediate SHH signal transduction, is overexpressed in GHomas and ACTHomas (73, 104). Here, GLI1 is linked to ACTH-producing pituitary gland adenoma.