Cushing disease
Meaning of Cushing disease: A small growth in the head drives glands above the kidneys, and the visible damage appears everywhere except where the fault lies.
Definition of Cushing disease
Cushing disease is the overproduction of cortisol caused by a benign tumor of the pituitary gland that releases too much adrenocorticotropic hormone. That hormone instructs the adrenal glands to make cortisol, so a small growth at the base of the brain drives two distant glands to flood the body with it. It is one specific cause of Cushing syndrome.
How does it differ from Cushing syndrome?
Cushing syndrome names the state of having too much cortisol, whatever the reason. Cushing disease names one reason. The distinction is not pedantry, because the source determines what can be done about it.
| Source of the excess | What is happening |
|---|---|
| Steroid medicine | A cortisol like drug taken for another condition; the commonest cause of all |
| Pituitary tumor | Cushing disease, driving the adrenal glands through an excess of signal |
| Adrenal tumor | The adrenal gland produces cortisol on its own, with no signal at all |
| Tumor elsewhere | A growth outside the pituitary, often in the lung, releasing the same signal |
What does prolonged cortisol excess do?
Cortisol acts on nearly every tissue, so the effects are scattered and can look unrelated. Fat is redistributed toward the trunk, the face and the back of the neck while the arms and legs thin, a pattern that separates it from ordinary weight gain. Skin becomes thin enough to bruise from small knocks, and wide purple stretch marks appear over the abdomen. Muscle wastes, most noticeably in the thighs, so rising from a low chair becomes difficult. High blood pressure and raised blood sugar develop, bone thins, wounds heal slowly, infections take hold more easily, periods become irregular, and mood and sleep are commonly disturbed.
How is the source pinned down?
In two steps. The first establishes that cortisol really is in excess, using tests that measure it across a full day, late at night when it should be at its lowest, or after a dose of steroid that would normally switch production off. The second locates the driver by measuring adrenocorticotropic hormone in the blood. A suppressed level points to the adrenal gland acting alone; a normal or raised level means something is still signaling, which narrows the search to the pituitary or a tumor elsewhere. Imaging of the pituitary follows, and where the scan is unclear, blood may be sampled directly from the veins draining the gland to confirm the signal is coming from there.
Also known as
Used in a sentence
Cushing disease was confirmed after imaging identified a pituitary adenoma associated with excess adrenocorticotropic hormone.
Good to know
Cushing disease refers specifically to Cushing syndrome caused by a pituitary tumor overproducing adrenocorticotropic hormone, distinguishing it from Cushing syndrome caused by steroid medication or a hormone-producing tumor elsewhere in the body.