The proposed role for GH in field cancerization may explain the increased propensity of acromegaly patients to develop colon, skin, thyroid, and prostate tumors (89,90), as well as the appearance of changes consistent with hepatocellular carcinoma (91-93) and mammary adenocarcinoma (94) in transgenic animal models of GH excess. Here, GH1 is linked to breast adenocarcinoma.