The adrenal glands, located in the cephalic pole of each kidney, are

formed by:

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• Cortex

• Marrow

 

Adrenal cortex and the adrenal medulla, whose endocrine functions

are distinct.

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Adrenal cortex 

 

The adrenal cortex produces

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• Glucocorticoids (mainly cortisol)

• Mineralocorticoids (mainly aldosterone)

• Androgens (mainly dehydroepiandrosterone (DHEA) and androstenedione)

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Glucocorticoids that promote and inhibit gene transcription in various cells, organs and systems. Prominent effects include anti-inflammatory actions and increased hepatic gluconeogenesis.

Mineralocorticoids that regulate the transport of electrolytes in the epithelia, particularly the renal conservation of sodium in exchange for potassium.

The main physiological action of adrenal androgens occurs after conversion to testosterone and dihydrotestosterone.

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Adrenal medulla

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The adrenal medulla consists of chromaffin cells, which synthesize and secrete catecholamines (mainly adrenaline and smaller amounts of norepinephrine). Chromaffin cells also produce bioactive amines and peptides (eg, histamine, serotonin, chromogranins, neuropeptide hormones). Adrenaline and norepinephrine, the main effector amines of the sympathetic nervous system, are responsible for the “attack or escape” response (ie, chronotropic and inotropic effects on the heart; bronchodilation; peripheral and splanchnic vasoconstriction with muscle vasodilation; metabolic effects including glycogenolysis, lipolysis and renin release).

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Clinical syndromes

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Most adrenal deficiency syndromes affect the release of all adrenocortical hormones. Hypofunction can be primary (dysfunction of the adrenal gland itself, as in Addison's disease ) or secondary (due to lack of adrenal stimulation by the pituitary or hypothalamus).

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Adrenal hyperfunction causes distinct clinical syndromes, depending on the hormone involved:

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• Hypersecretion of glucocorticoids results in Cushing's syndrome.

• Hypersecretion of aldosterone results in hyperaldosteronism.

• Hypersecretion of androgens results in adrenal virilism.

• Hypersecretion of adrenaline and norepinephrine results in pheochromocytoma .

 

These syndromes often have overlapping characteristics.

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Hyperfunction may be compensatory, as in congenital adrenal hyperplasia , or due to acquired hyperplasia, adenomas or adenocarcinomas.

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Adrenal is not uncommon for tumors to develop. These tumors are usually discovered at random, a situation in which we call an adrenal incidentaloma.

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