Cushing syndrome

Cushing syndrome is due to the effects of excessive glucocorticoids which may be exogenous or endogenous.


In modern Western populations, iatrogenic steroid administration for treatment of inflammatory condition is the most common cause, e.g. asthma, rheumatoid arthritis.

Endogenous sources of excess cortisol production include:

The work up of Cushing syndrome requires measurement both of cortisol as well as ACTH. Measuring cortisol typically needs to be over a 24 hour period because release is intermittent. 

Radiographic features

Imaging of the suspected region is then required:

If ACTH is elevated but no microadenoma can be identified, and no ectopic source can be found, then inferior petrosal sinus sampling can be undertaken. Bilateral adrenal hyperplasia is one of the most common findings on abdominal CT.

ACTH secreting pituitary microadenomas may be unapparent on imaging in 40-50% of cases.

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