Adrenal gland: structure, hormones, and clinical significance

Anatomy and internal organization

Each adrenal gland is divided into two anatomically and functionally distinct regions. The outer layer, the adrenal cortex, is composed of steroid-producing cells arranged in zones. The inner core, the adrenal medulla, contains chromaffin cells that release catecholamines. These two parts arise from different embryological tissues and therefore produce different types of chemical messengers.

Major hormones and their roles

The cortex synthesizes steroid hormones in three broad groups: mineralocorticoids, glucocorticoids and adrenal androgens. Mineralocorticoids (for example, aldosterone) help regulate blood pressure and the balance of sodium and potassium that determine electrolyte homeostasis. Glucocorticoids (notably cortisol) influence carbohydrate and protein metabolism, inflammation, and the body’s response to stress. The medulla produces catecholamines such as adrenaline and noradrenaline, which provide rapid cardiovascular and metabolic adjustments in fight-or-flight situations.

• Mineralocorticoids: regulate fluid and salt handling (mineralocorticoids).
• Glucocorticoids: modulate metabolism and immune responses (glucocorticoids, cortisol).
• Androgens: weak sex steroids produced in small amounts (androgens).
• Catecholamines: rapid-acting mediators of alertness and circulation (hormones of the medulla).

Development, variation and evolutionary notes

The cortex and medulla have distinct embryonic origins: the cortex arises from mesodermal tissue while the medulla is derived from neural crest cells. Across vertebrates the position and microscopic arrangement can vary, and in humans the suprarenal position atop the kidney is a characteristic feature. The glands are often referred to as suprarenal glands in anatomical texts.

Clinical importance and common disorders

Because of the adrenals’ role in hormone production, dysfunction can lead to a range of medical conditions. Primary adrenal insufficiency (Addison disease) causes inadequate steroid secretion; chronic excess glucocorticoid exposure results in Cushing-like features; catecholamine-secreting tumors of the medulla (pheochromocytomas) provoke episodic hypertension and palpitations; congenital enzyme defects in steroid synthesis lead to congenital adrenal hyperplasia with altered androgen levels. Evaluation of adrenal function uses biochemical tests and imaging when indicated.

Why the adrenal glands matter

The adrenal glands integrate short-term responses such as the release of adrenaline with longer-term regulation via steroids that shape metabolism, immune function and fluid balance. That interplay is central to surviving acute threats and maintaining homeostasis. For further reading on anatomy, physiology and clinical aspects, consult specialized endocrinology sources or medical references (steroid pathways, electrolyte effects, blood pressure control). Additional introductory materials are available through general anatomy and physiology overviews (adrenal gland, kidney relationships, comparative anatomy).

Note: this article summarizes widely accepted anatomical and physiological concepts and is intended for general information rather than clinical guidance. For diagnosis or treatment decisions seek professional medical advice and up-to-date clinical sources (hormones and stress response; cortisol regulation).