adrenal cortex
Meaning of adrenal cortex: The outer rind of the gland sitting on each kidney, built in three layers that turn cholesterol into three different classes of hormone.
Definition of adrenal cortex
The adrenal cortex is the outer shell of the adrenal gland, the small triangular organ capping each kidney. It is arranged in three layers, and each makes a different class of steroid hormone: one governing salt and water balance, one governing the stress response and the handling of sugar, and one contributing weak sex hormones. All of them are built from cholesterol.
What does each layer make?
| Layer | Hormone | What it controls |
|---|---|---|
| Outermost | Aldosterone | Sodium retention, potassium loss, blood pressure |
| Middle | Cortisol | Blood sugar, stress response, inflammation |
| Innermost | Weak male-type hormones | A minor contribution to sex hormone supply |
The layers are visibly different under the microscope, and each holds a different set of enzymes, which is why the same starting material comes out as three unrelated products. A block in one enzyme diverts the whole assembly line toward whichever branch remains open, which is what happens in the inherited conditions grouped as congenital adrenal hyperplasia.
How is it different from the inside of the gland?
Almost entirely. The adrenal medulla at the center is not glandular tissue at all in origin but nervous tissue, wired directly into the sympathetic nerves, and it releases adrenaline within seconds of a signal. The cortex works on a slower chemical timescale and answers to hormones in the blood. Two organs of quite different ancestry ended up packaged in one capsule, and only their being neighbors gives the adrenal gland its appearance of being a single structure.
What controls it?
Not one signal but two, and this catches people out. Cortisol and the weak sex hormones are driven by a message from the pituitary gland, rising and falling on a daily rhythm and surging in illness or injury. Aldosterone answers mainly to a separate system run from the kidney that senses blood pressure and salt, and to the potassium level directly. The consequence is that pituitary failure starves the middle and inner layers while leaving salt handling largely intact, whereas destruction of the cortex itself removes both, producing low blood pressure and salt loss alongside the loss of cortisol.
Used in a sentence
Imaging showed thickening of the adrenal cortex on both sides.
Good to know
Cortisol production depends on the pituitary signal while aldosterone answers mainly to the kidney's own pressure and salt sensing, so pituitary failure leaves salt handling largely intact whereas destruction of the cortex itself removes both.
Word origin
Where “adrenal cortex” comes from
Adrenal joins the Latin ad-, meaning near, to renes, meaning kidneys, and cortex is the Latin word for bark or rind, used for the outer layer of an organ.