This hypothesis was further confirmed measuring the in vitro basal secretion of CXCL12 by human pituitary adenoma primary cultures resulting in an autocrine constitutive stimulation of DNA synthesis [129] (Figure 2) and, indirectly, by the absence of CXCR4 activating mutations in GH-secreting and NFPA able to sustain adenoma cell proliferation [204]. This evidence concerns the gene CXCL12 and adenoma.