One adrenal gland sits on top of each kidney. Each has two parts that act like separate glands: an outer cortex and an inner medulla.
Cortisol
The cortex releases cortisol under the control of ACTH. Cortisol raises blood glucose, supports blood pressure and dampens inflammation, and it peaks in the early morning.
Aldosterone
The cortex also makes aldosterone, driven mainly by the renin-angiotensin system and by high potassium. It makes the kidneys keep sodium and water and lose potassium.
Adrenaline and noradrenaline
The medulla is part of the sympathetic nervous system. Within seconds it releases adrenaline, which raises heart rate, blood pressure and blood glucose and opens the airways.
The stress response
Acute stress uses adrenaline for speed and cortisol for endurance. Long-term high cortisol, from disease or steroid medicines, causes weight gain, thin skin, high glucose and weak bones.
At the bedside
A patient on long-term steroids who stops them suddenly or becomes very ill can go into adrenal crisis, with low blood pressure that does not respond to fluids. Check the medication list and give stress-dose steroids as ordered.
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Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).