Adrenal glands
Also known as: suprarenal glands
The adrenal glands are paired endocrine glands sitting atop each kidney. The outer cortex secretes aldosterone, cortisol, and androgens, while the inner medulla secretes the catecholamines epinephrine and norepinephrine.
The adrenal (suprarenal) glands are small, triangular endocrine glands perched on the superior pole of each kidney. Each gland has two functionally distinct parts: an outer cortex derived from mesoderm and an inner medulla derived from neural crest tissue — essentially a modified sympathetic ganglion.
The cortex has three zones, remembered as GFR from outside in. The zona glomerulosa secretes the mineralocorticoid aldosterone, which acts on the kidney to retain sodium and water and excrete potassium under the control of the renin-angiotensin-aldosterone system. The zona fasciculata secretes the glucocorticoid cortisol, which raises blood glucose, mobilizes fuel, and suppresses inflammation under control of pituitary ACTH. The zona reticularis secretes androgens such as DHEA. A common mnemonic pairs the zones with "salt, sugar, sex."
The medulla releases epinephrine and norepinephrine directly into the bloodstream when the sympathetic nervous system fires, driving the fight-or-flight response: faster heart rate, bronchodilation, and glucose release. These same hormones matter in exercise physiology, where acute catecholamine and cortisol responses to training influence force production and fuel use. Clinically, cortical dysfunction produces disorders such as Cushing's syndrome (cortisol excess) and Addison's disease (cortical insufficiency).
The adrenal glands are tested across several credentialing exams: USMLE Step 1 emphasizes the zonation, hormone pathways, and their pathologies; the CSCS exam covers catecholamine and cortisol responses to resistance exercise; and the NPTE-PTA touches on endocrine and metabolic system disorders relevant to rehabilitation.
Key takeaways
- The adrenal glands sit on top of the kidneys and consist of an outer cortex and an inner medulla.
- The cortex zones (glomerulosa, fasciculata, reticularis) secrete aldosterone, cortisol, and androgens — "salt, sugar, sex."
- The medulla is neural crest-derived and secretes epinephrine and norepinephrine during sympathetic activation.
- Aldosterone is regulated by the renin-angiotensin-aldosterone system, while cortisol is regulated by pituitary ACTH.
- USMLE Step 1 tests adrenal zonation and pathology, while the CSCS exam covers hormonal responses to exercise.