GHRL and breast cancer: It has been confirmed that the stomach was indeed not the only source of ghrelin (13); hypothalamus, hippocampus, pituitary gland, cortex, small intestine, and pancreas can also secrete a small amount of ghrelin (14–16), GHRL plays important roles in the development of tumors, and aberrant GHRL expression has been found in various cancers, such as breast cancer (17), lung cancer (18), bladder cancer (19), and adrenal cancer (20).