The adrenal glands are paired retroperitoneal organs that play a critical role in endocrine and neurocrine function. These are small structures that weigh 5-7 grams, measure 4-6 cm by 2-3 cm, and are located within Gerota’s fascia above each kidney. The adrenal gland is composed of two distinct regions; the cortex (outer layer) and medulla (inner layer). These regions have different embryologic origins resulting in distinct functions. The adrenal cortex arises from the intermediate mesoderm of the urogenital ridge between weeks 5-8 and has purely endocrine function. The cortex is comprised of three zones with distinct endocrine functions: zona glomerulosa (which produces mineralocorticoids such as aldosterone), zona fasciculata (which produces glucocorticoids such as cortisol), and the zona reticularis (which produces sex steroids such as estrogens/androgens).The adrenal medulla develops from neural crest cells from the adjacent sympathetic ganglia in the 9th week of embryonal development and has purely neurocrine function. The adrenal medulla, which accounts for only about 10% of the gland, is composed of chromaffin cells innervated by pre-ganglionic sympathetic fibers from T11-L2. The medulla secretes catecholamines (epinephrine/norepinephrine/dopamine) which are derived from the amino acid tyrosine.1 Due to the diverse function of the adrenal gland, neoplastic processes of the gland often result in clinical stigmata related to excess hormone production.
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