ABSTRACT
Background The adrenal glands are two small retroperitoneal organs composed of a cortex and a medulla. These components are of entirely different tissue embryologically, histologically, and functionally. The cortex is responsible for the synthesis and excretion of adrenal steroid hormones and is divided into three histological and functional zones. The outer zone produces the principal mineralocorticoid aldosterone, the middle zone produces glucocorticoids, primarily cortisol, and the inner zone the androgenic hormones androstenedione and dehydroepiandrosterone (DHEA, and the sulfate DHEAS). Growth and secretory functions of cortisol and adrenal androgenic hormones are controlled by the anterior pituitary adrenocorticotropic hormone (ACTH). Aldosterone secretion is controlled by extracellular sodium concentration, blood volume, and the renin-angiotensin-aldosterone system (RAAS) via angiotensin 2. Cholesterol is the principal metabolic precursor of the adrenocortical steroids. Consequently, cholesterol analogs are used for adrenal scintigraphy.1-3
The adrenal medulla is embryologically derived from the neural crest, and is a part of the sympathetic nervous system. The adrenal medulla secrets the catecholamines epinephrine and norepinephrine. Radiolabeled catecholamine analogs are used for scintigraphic imaging of tumors deriving from the sympathetic nervous system.2-4
Adrenocortical tumors The hypersecretion of different steroid hormones leads to different clinical symptoms and syndromes.1
