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 adenoma they are non-secreting adenomas. While pituitary adenomas are common, affecting approximately one in 6 of the general population, clinically active pituitary adenomas that require surgical treatment are more rare, affecting approximately one in 1000 of the general population. Hormone secreting pituitary adenomas cause one of several forms of hyperpituitarism. The specifics depend on the type of hormone. Some tumors secrete more than one hormone, the most common combination being GH and prolactin, which present as unexpected bone growth and unexpected lactation (in both men and women). A patient with pituitary adenoma may present with visual field defects, classically bitemporal hemianopsia.