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
Pituitary apoplexy or nonsecretory tumors, which do not produce excessive amounts of hormones; this might explain why the tumor has often gone undetected prior to an episode of apoplexy. The first case description of pituitary apoplexy has been attributed to the American neurologist Pearce Bailey in 1898. This was followed in 1905 by a further report from the German physician Bleibtreu. Surgery for pituitary apoplexy was described in 1925. Before the introduction of steroid replacement, the mortality from pituitary apoplexy approximated 50%. The name of the condition was coined in 1950 in a case series by physicians from Boston City Hospital and