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Diagnosis of Cushing's syndrome

Last edited 20 Apr 2021. Last reviewed 12 Jul 2023

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Diagnosis of Cushing's syndrome

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Who should be tested

Testing for Cushing's syndrome is recommended in the following groups (1):

Patients with unusual features for age (e.g. osteoporosis, hypertension)

Patients with multiple and progressive features, particularly those who are more predictive of Cushing's syndrome

*Features that best discriminate Cushing's syndrome; most do not have a high sensitivity*
	easy bruising
	facial plethora
	proximal myopathy (or proximal muscle weakness)
	striae (especially if reddish purple and > 1 cm wide)
	on children, weight gain with decreasing growth velocity

*Cushing's syndrome features in the general population that are common and/or less discriminatory*
depression	dorsocervical fat pad ("buffalo hump")
fatigue	facial fullness
weight gain	obesity
back pain	supraclavicular fullness
changes in appetite	thin skin
decreased concentration	peripheral edema
decreased libido	acne
impaired memory (especially short term)	hirsutism or female balding
insomnia	poor skin healing
irritability
menstrual abnormalities
in children, slow growth	in children, abnormal genital virilization
	in children, short stature
	in children, pseudoprecocious puberty or delayed puberty

children with decreasing height percentile and increasing weight

patients with adrenal incidentaloma compatible with adenoma

The following tests are advised NOT to be used to test for Cushing's syndrome (1)

random serum cortisol or plasma ACTH levels

urinary 17-ketosteroids

insulin tolerance test

loperamide test

tests designed to determine the cause of Cushing's syndrome (e.g. pituitary and adrenal imaging, 8 mg DST)

For the initial testing for Cushing's syndrome, one of the following tests based on its suitability for a given patient, is recommended (1):

urine free cortisol (UFC; at least two measurements)

late-night salivary cortisol (two measurements)

1-mg overnight dexamethasone suppression test (DST)

longer low-dose DST (2 mg/d for 48 h)

Diagnostic criteria that suggest Cushing's syndrome are UFC greater than the normal range for the assay, serum cortisol greater than 1.8 mug/dl (50 nmol/liter) after 1 mg dexamethasone (1-mg DST), and late-night salivary cortisol greater than 145 ng/dl (4 nmol/liter).

Subsequent evaluation based on expert advice

Reference:

Nieman LK et al. The Diagnosis of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline.J Clin Endocrinol Metab. 2008 May; 93(5): 1526-1540.

Identification of cause of Cushing's syndrome

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Diagnosis of Cushing's syndrome

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