CDKN1B and neoplasm: The diagnosis of pituitary hyperplasia should normally prompt the investigation of a GHRH-secreting tumor (see below), but if none is identified, the diagnosis of primary pituitary hyperplasia should lead the treating physician to consider the possibility of an underlying germline genetic predisposition syndrome, such as MEN1/MEN4, Carney Complex, McCune Albright and X-LAG syndrome [55,65,66,67,68,69].