GHRH and pituitary gland adenoma: There are three main hypotheses about the pathogenesis of these tumors: (1) Excess GHRH produced by primary gangliocytoma stimulates the adenomatous formation (36); (2) Both ganglion cells and adenoma cells might arise from a common stem/progenitor cell (37); (3) The neuronal component originates from neuronal differentiation of a preexisting pituitary adenoma (38).