Hypothalamic–pituitary–adrenal axis Hypothalamic–pituitary–adrenal axis The hypothalamic–pituitary–adrenal axis (HPA axis or HTPA axis) is a complex set of direct influences and feedback interactions among three components: the hypothalamus, the pituitary gland (a pea-shaped structure located below the thalamus), and the adrenal (also called "suprarenal") glands (small, conical organs on top of the kidneys). These organs and their interactions constitute the HPA axis, a major neuroendocrine system that controls reactions to stress and regulates many body processes, including digestion, the immune system, mood and emotions, sexuality, and energy storage and expenditure. It is the common mechanism for interactions among glands, hormones, and parts of
Anterior pituitary anterior pituitary contains five types of endocrine cell, and they are defined by the hormones they secrete: somatotropes (GH); Lactotropes (PRL); gonadotropes (LH and FSH); corticotropes (ACTH) and thyrotropes (TSH). It also contains non-endocrine folliculostellate cells which are thought to stimulate and support the endocrine cell populations. Hormones secreted by the anterior pituitary are trophic hormones (Greek: trophe, “nourishment”) and tropic hormones. "Trophic hormones" directly affect growth either as hyperplasia or hypertrophy on the tissue it is stimulating. "Tropic hormones" are named for their ability to act directly on target tissues or other endocrine glands to release hormones, causing numerous