In conclusion, apelin/APJ system, as a novel activity regulator, is involved in the regulation of neurohumoral fluid in the endocrine system, especially the hypothalamic-pituitary axis. In this review, we summarize the expression of apelin and APJ in the hypothalamus, pituitary, thyroid, adrenal, ovarian, and testicular tissues. In addition, we further explored its effect on endocrine diseases by affecting these signal axes. It is worthy of our attention that the difference in apelin