The hypothalamic–pituitary–adrenal axis (HPA axis or HTPA axis), also known as the limbic–hypothalamic–pituitary–adrenal axis (LHPA axis) and, occasionally, as the hypothalamic–pituitary–adrenal–gonadotropic axis, is a complex set of direct influences and feedback interactions among three endocrine glands: the hypothalamus, the pituitary gland (a pea-shaped structure located below the hypothalamus), and the adrenal (also called "suprarenal") glands (small, conical organs on top of the kidneys).