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 who could be treated conservatively. After an episode of pituitary apoplexy, 80% of people develop hypopituitarism and require some form of hormone replacement therapy. The most common problem is growth hormone deficiency, which is often left untreated but may cause decreased muscle mass and strength, obesity and fatigue. 60–80% require hydrocortisone replacement (either permanently or when unwell), 50–60% need thyroid hormone replacement, and 60–80% of men require testosterone supplements. Finally, 10–25% develop diabetes insipidus, the inability to retain fluid in the kidneys due to a lack of the pituitary antidiuretic hormone. This may be treated with the drug desmopressin, which