Adrenal

Adrenal refers to the adrenal glands, a pair of small, triangular endocrine glands located on the superior poles of the kidneys. Each gland has an outer cortex and an inner medulla. The cortex synthesizes steroid hormones: mineralocorticoids such as aldosterone; glucocorticoids such as cortisol; and androgens. Aldosterone helps regulate sodium and potassium balance and blood pressure through the renin-angiotensin system. Cortisol affects metabolism, immune function, and the stress response. The medulla produces catecholamines, mainly epinephrine and norepinephrine, released in response to sympathetic activity, producing rapid physiological changes during stress.

Regulation: The cortex is regulated mainly by adrenocorticotropic hormone (ACTH) from the pituitary, while aldosterone secretion is influenced by the renin-angiotensin system and potassium levels. The medulla is innervated directly by sympathetic nerve fibers.

Clinical relevance: Diseases include Addison's disease (adrenal insufficiency) and Cushing syndrome (excess cortisol), pheochromocytoma (catecholamine-secreting tumor of the medulla), and primary hyperaldosteronism (excess aldosterone). Congenital adrenal hyperplasia involves enzymatic defects in cortisol synthesis. Adrenal masses may be discovered incidentally on imaging.