The Biochemical Investigation of Cushing Syndrome

Marie Simard, M.D.


Neurosurg Focus. 2004;16(4) 

In This Article

Abstract and Introduction


Cushing syndrome is an insidious illness that warrants an early diagnosis to avoid the effects of prolonged hypercortisolism. The variability in the clinical features of the disease and the occasional inconsistencies between different biochemical tests performed to identify it render the diagnosis challenging. In this paper the author discusses the various biochemical tests that are useful for the diagnoses of Cushing syndrome and Cushing disease, with an emphasis on the respective sensitivities and specificities of these tests. The measurement of evening salivary cortisol and the combined low-dose dexamethasone—corticotropin-releasing hormone stimulation test have improved overall sensitivity and specificity in the evaluation of Cushing syndrome and Cushing disease.


A diagnosis of Cushing syndrome, unless unequivocal, is often a challenge for the clinician. The signs and symptoms of Cushing syndrome are often subtle during the initial stage of the illness. Cushing syndrome may present as an episodic hypercortisolism that is associated with fluctuating clinical findings; however, due to the detrimental effects of prolonged hypercortisolism on body tissues, early detection of the disorder is essential.[20] In this paper I will review the various screening tests used to determine hypercortisolism (Cushing syndrome) and the biochemical evaluation performed to identify a pituitary ACTH-secreting adenoma (Cushing disease).