diagnosis of Cushing's syndrome

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