The adrenal glands, located on the cephalad portion of each kidney (see figure Adrenal glands Adrenal glands 
), consist of a
Cortex
Medulla
The adrenal cortex and adrenal medulla each have separate endocrine functions.
Adrenal glands
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Adrenal cortex
The adrenal cortex produces
Glucocorticoids (primarily cortisol)
Mineralocorticoids (primarily aldosterone)
Androgens (primarily dehydroepiandrosterone and androstenedione)
Glucocorticoids promote and inhibit gene transcription in many cells and organ systems. Prominent effects include anti-inflammatory actions and increased hepatic gluconeogenesis.
Mineralocorticoids regulate electrolyte transport across epithelial surfaces, particularly renal conservation of sodium in exchange for potassium.
Adrenal androgens’ chief physiologic activity occurs after conversion to testosterone and dihydrotestosterone.
The physiology of the hypothalamic-pituitary-adrenocortical system Overview of the Endocrine System The endocrine system coordinates functioning between different organs through hormones, which are chemicals released into the bloodstream from specific types of cells within endocrine (ductless)... read more is further discussed elsewhere.
Adrenal medulla
The adrenal medulla is composed of chromaffin cells, which synthesize and secrete catecholamines (mainly epinephrine and lesser amounts of norepinephrine). Chromaffin cells also produce bioactive amines and peptides (eg, histamine, serotonin, chromogranins, neuropeptide hormones). Epinephrine and norepinephrine, the major effector amines of the sympathetic nervous system, are responsible for the “flight or fight” response (ie, chronotropic and inotropic effects on the heart; bronchodilation; peripheral and splanchnic vasoconstriction with skeletal muscular vasodilation; metabolic effects including glycogenolysis, lipolysis, and renin release).
Clinical syndromes
Most adrenal deficiency syndromes affect output of all adrenocortical hormones. Hypofunction may be primary (malfunction of the adrenal gland itself, as in Addison disease Addison Disease Addison disease is an insidious, usually progressive hypofunctioning of the adrenal cortex. It causes various symptoms, including hypotension and hyperpigmentation, and can lead to adrenal crisis... read more 
) or secondary (due to lack of adrenal stimulation by the pituitary or hypothalamus). Some experts refer to hypothalamic malfunction as tertiary.
Adrenal hyperfunction causes distinct clinical syndromes depending on the hormone involved:
Hypersecretion of epinephrine and norepinephrine results in symptoms of pheochromocytoma Pheochromocytoma A pheochromocytoma is a catecholamine-secreting tumor of chromaffin cells typically located in the adrenals. It causes persistent or paroxysmal hypertension. Diagnosis is by measuring catecholamine... read more .
These syndromes frequently have overlapping features.
Hyperfunction may be compensatory, as in congenital adrenal hyperplasia Overview of Congenital Adrenal Hyperplasia Congenital adrenal hyperplasia is a group of genetic disorders, each characterized by inadequate synthesis of cortisol, aldosterone, or both. In the most common forms, accumulated hormone precursors... read more , or due to acquired hyperplasia, adenomas, or adenocarcinomas.
