Cushing syndrome
Meaning of Cushing syndrome: By a wide margin the most common cause is steroid medication taken for another illness rather than a tumor.
Definition of Cushing syndrome
Cushing syndrome is the collection of changes produced by prolonged exposure to too much cortisol, the hormone made by the outer layer of the adrenal glands. Cortisol governs how the body handles sugar, fat and protein, helps hold blood pressure up and damps down inflammation, so a sustained excess of it disturbs many systems at once.
What causes it?
| Source | What is happening |
|---|---|
| Steroid medication | Glucocorticoids taken for asthma, arthritis, bowel disease or after transplant; much the most common cause |
| Pituitary tumor | A small benign growth pours out adrenocorticotropic hormone, driving both adrenal glands; this is Cushing disease |
| Adrenal tumor | A growth in one adrenal gland makes cortisol on its own account |
| Ectopic source | A tumor elsewhere, often in the lung, produces the pituitary hormone abnormally |
Separating these is the whole business of evaluation, because the first step is establishing that cortisol really is high, and the second is finding where the drive is coming from. Blood levels of the pituitary hormone point the way: high with a pituitary or ectopic source, suppressed when an adrenal tumor is making cortisol independently.
How does it show itself?
Cortisol moves fat toward the trunk, face and back of the neck while breaking down protein in the limbs, producing the characteristic pattern of central weight gain with thinning arms and legs and a rounded, fuller face. Skin becomes thin and bruises with little provocation, and wide purplish stretch marks appear over the abdomen, thighs or upper arms. Muscles weaken, most noticeably in the shoulders and hips, so rising from a chair becomes difficult. Blood pressure and blood sugar rise, bone thins, wounds heal slowly, infections take hold more easily, mood and sleep are disturbed, and menstrual cycles become irregular. Not every feature appears in every person, and several of them are common in the general population, which is what makes the diagnosis less obvious than the textbook picture suggests.
Why is Cushing disease not the same thing?
Cushing syndrome names the state of cortisol excess whatever its source. Cushing disease names one specific cause of it, a pituitary tumor secreting the hormone that drives the adrenal glands. Every case of Cushing disease is a case of Cushing syndrome; most cases of Cushing syndrome are not Cushing disease. The names are similar enough to be swapped by accident in ordinary conversation, but they point at different levels of the same hormonal chain.
Also known as
Used in a sentence
The patient's constellation of findings prompted evaluation for Cushing syndrome.
Good to know
Cushing syndrome caused by steroid medication is distinguished from the syndrome driven by a hormone-producing tumor, since identifying the source of the excess cortisol determines the entire course of evaluation.