Adrenal Hyperfunction - Cushing Syndrome

  • Diagnosis
  • Algorithms
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Resistant diabetes, refractory hypertension, or multiple signs/symptoms of Cushing syndrome after ruling out metabolic syndrome or polycystic ovarian syndrome (PCOS)
  • Do not test patients who have hypercortisolism secondary to administration of glucocorticoids (oral, inhaled, injections, topical)

Laboratory Testing

  • Initial testing (Endocrine Society, 2008; NCCN, 2016)
    •  Salivary cortisol (collected between 2300 hours and midnight) – at least 2 measurements
      • Reflects circadian nadir so elevations are more relevant
      • Salivary samples are stable over time
      • Counsel individual to collect on quiet, restful evening
      • Cutoff values are test and age specific
    • 24-hour urine free cortisol (UFC) – at least 2 measurements
      • 24-hour urine collection – random measurements not recommended
      • Urinary cortisol levels >3 times the upper limit of normal are unequivocal and confirm diagnosis
      • Results not affected by taking oral estrogen
    • Dexamethasone suppression testing (DST) – overnight and 2-day tests are available
      • Does not interfere with cortisol tests; other glucocorticoids will influence cortisol levels and must be discontinued prior to testing
        • Other hormones that may interfere with cortisol testing – exogenous testosterone, Nature-Throid, estrogens (eg, birth control), megestrol acetate
        • Estrogen-containing drugs should be withdrawn for 6 weeks prior to testing
      • Low-dose (1 mg) DST
        • Patient should take 1 mg dexamethasone between 2300 hours and 2400 hours
        • Goal – should suppress adrenocorticotropic hormone (ACTH) production if hypothalamic-pituitary-adrenal axis (HPA) is normal
        • Serum or urine should be collected between 0800 and 0900 hours and tested for free cortisol
          • ACTH collected at same time may be helpful in case of positive test
        • Dexamethasone is measured to confirm administration and normal metabolism
      • 2-day, 2 mg test – may be used to confirm that ACTH can be suppressed if overnight, low-dose test is equivocal
        • Administer 0.5 mg every 6 hours starting at 0800 for 2 days for a total of 8 doses (2 mg)
        • Collect serum for cortisol 2-6 hours after last dose administered
        • Collecting ACTH at same time will assist with etiology in case of positive test
        • Collect dexamethasone to confirm administration and normal metabolism
        • Urinary corticosteroid excretion on day 2 of dexamethasone administration has been used (compare to baseline day urinary corticosteroid excretion)
          • Not currently recommended, but literature often cites concentrations
      • To confirm elevated results – repeat either of the DST tests or the cortisol tests
        • If high suspicion remains – use high-dose dexamethasone (8 mg) overnight test
          • Similar protocol to low-dose overnight dexamethasone suppression test
          • Negative suppression testing – suggests etiology other than Cushing syndrome
  • Follow-up testing (Endocrine Society, 2008; NCCN, 2016)
    • Endocrinology referral
    • Serum ACTH in conjunction with suppression tests – aid in determining whether disease is adrenal, pituitary, or ectopic ACTH-based
      • If ACTH is suppressed (<10 pg/mL) – suggests etiology is ACTH independent and pathology is adrenal (adenoma, carcinoma)
        • Refer to Imaging Studies section
      • If ACTH is >20 pg/mL (high levels) – suggests ectopic ACTH
        • Refer to Imaging Studies section
      • If ACTH is intermediate between these levels – likely Cushing syndrome and magnetic resonance imaging (MRI) should be done to visualize tumor
        • ACTH-producing tumors are often not visualized (microadenoma)
        • Bilateral inferior petrosal sinus sampling is indicated (Pappachan, 2017)
          • Note: this is technically difficult and should only be performed in high-volume center
            • Petrosal ACTH to serum ACTH ratio is measured before and after corticotropin stimulation
            • Absence of change in gradient – suggestive of ectopic ACTH-producing tumor
            • Significant increase in pre- and poststimulation – expected in Cushing syndrome

Histology

  • Pathology review of specimen (biopsy tumor) to classify type of tumor
    • Immunohistochemistry stain – ACTH stain most common

Imaging Studies

  • MRI pituitary with inferior bilateral petrosal sampling of ACTH to differentiate between Cushing syndrome and ectopic source (if necessary)
    • If ACTH is low – MRI of adrenal glands
    • If ACTH >20 pg/mL – search for ectopic ACTH-secreting tumor
  • CT adrenal protocol or MRI adrenals – to identify unilateral/bilateral tumor or hyperplasia

Prognosis

  • Untreated Cushing syndrome – associated with excess morbidity/mortality secondary to cardiovascular disease
  • If tumor is benign and removed – mortality associated with comorbid diseases developed in association with tumor may normalize
  • Malignant tumors producing ACTH have a poor prognosis

Differential Diagnosis

Adrenal hyperfunction (Cushing syndrome) causes excess cortisol secretion by the adrenal gland and is manifested by a constellation of symptoms, including central obesity, hypertension, type 2 diabetes, easy bruisability, abdominal striae, and myopathy. These signs and symptoms of high cortisol are common and nonspecific, making the diagnosis challenging.

Epidemiology

  • Incidence – 2-3/100,000 (Endocrine Society, 2008)
  • Age – uncommon in children; peaks in 20s-50s
  • Sex – M<F, 1:4-6

Etiology

  • Endogenous
    • Pituitary (Cushing syndrome)
      • Hyperplasia
      • Adenoma, often microadenoma
    • Adrenal
      • Adenoma
      • Carcinoma – most are sporadic tumors
        • Hereditary syndromes (eg, Li-Fraumeni) may present as carcinoma
    • Ectopic production of adrenocorticotropic hormone (ACTH)
  • Exogenous
    • Glucocorticoid administration
  • Genetics (Lacroix, 2015)
    • Pituitary adenoma
      • USP8, MEN1, CDKNB/p27Kip1, AIP, DICER1
    • Ectopic ACTH secretion
      • RET, MEN1
    • Bilateral macronodular adrenal hyperplasia
      • ARMC5, MEN1, FH, GNAS1, PDE11A, PDE88, MC2R, PRKACA
    • Adrenal adenoma
      • PRKACA, CTNNB1, GNAS1, PRKAR1A
    • Primary pigmented nodular adrenocortical disease
      • PRKAR1A, PDE11A, PDE8B, PRKACA

Pathophysiology

  • Corticotropin-releasing hormone (CRH) in the hypothalamus stimulates release of ACTH from the pituitary gland
  • ACTH acts on the adrenal glands to produce cortisol
  • Most endogenous cases are caused by hypersecretion of pituitary ACTH or ectopic production of ACTH from nonpituitary source

Clinical Presentation

  • Centripetal obesity, moon facies, buffalo hump, hirsutism, reddish-purple striae
  • Hypertension
  • Menstrual abnormalities (eg, amenorrhea)
  • Irritability, impaired memory
  • Osteoporosis
  • Fatigue, weakness
  • Proximal myopathy
  • Impaired glucose tolerance
Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Cortisol, Saliva 0081117
Method: Quantitative Enzyme Immunoassay

Limitations 

Do not use for patients taking glucocorticoids

Cortisol Urine Free by LC-MS/MS 0097222
Method: Quantitative Liquid Chromatography-Tandem Mass Spectrometry

Limitations 

Do not use for patients taking glucocorticoids

Cortisol, Serum 0070030
Method: Quantitative Chemiluminescent Immunoassay

Guidelines

NCCN Clinical Practice Guidelines in Oncology, Neuroendocrine Tumors. National Comprehensive Cancer Network. Fort Washington, PA [Accessed: Aug 2017]

Nieman LK, Biller BM, Findling JW, Newell-Price J, Savage MO, Stewart PM, Montori VM. The diagnosis of Cushing's syndrome: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2008; 93(5): 1526-40. PubMed

General References

Alexandraki KI, Grossman AB. Novel insights in the diagnosis of Cushing's syndrome. Neuroendocrinology. 2010; 92 Suppl 1: 35-43. PubMed

Batista DL, Riar J, Keil M, Stratakis CA. Diagnostic tests for children who are referred for the investigation of Cushing syndrome. Pediatrics. 2007; 120(3): e575-86. PubMed

Bertagna X, Guignat L, Groussin L, Bertherat J. Cushing's disease. Best Pract Res Clin Endocrinol Metab. 2009; 23(5): 607-23. PubMed

Elamin MB, Murad H, Mullan R, Erickson D, Harris K, Nadeem S, Ennis R, Erwin PJ, Montori VM. Accuracy of diagnostic tests for Cushing's syndrome: a systematic review and metaanalyses. J Clin Endocrinol Metab. 2008; 93(5): 1553-62. PubMed

Findling JW, Raff H. Cushing's Syndrome: important issues in diagnosis and management. J Clin Endocrinol Metab. 2006; 91(10): 3746-53. PubMed

Guaraldi F, Salvatori R. Cushing syndrome: maybe not so uncommon of an endocrine disease. J Am Board Fam Med. 2012; 25(2): 199-208. PubMed

Jehle S, Walsh JE, Freda PU, Post KD. Selective use of bilateral inferior petrosal sinus sampling in patients with adrenocorticotropin-dependent Cushing's syndrome prior to transsphenoidal surgery. J Clin Endocrinol Metab. 2008; 93(12): 4624-32. PubMed

Lacroix A, Feelders RA, Stratakis CA, Nieman LK. Cushing's syndrome Lancet. 2015; 386(9996): 913-27. PubMed

Newell-Price J. Diagnosis/differential diagnosis of Cushing's syndrome: a review of best practice. Best Pract Res Clin Endocrinol Metab. 2009; 23 Suppl 1: S5-14. PubMed

Pappachan JM, Hariman C, Edavalath M, Waldron J, Hanna FW. Cushing's syndrome: a practical approach to diagnosis and differential diagnoses. J Clin Pathol. 2017; 70(4): 350-359. PubMed

Pivonello R, De Martino MC, De Leo M, Lombardi G, Colao A. Cushing's Syndrome. Endocrinol Metab Clin North Am. 2008; 37(1): 135-49, ix. PubMed

Raff H. Cushing's syndrome: diagnosis and surveillance using salivary cortisol. Pituitary. 2012; 15(1): 64-70. PubMed

Turpeinen U, Hämäläinen E. Determination of cortisol in serum, saliva and urine. Best Pract Res Clin Endocrinol Metab. 2013; 27(6): 795-801. PubMed

References from the ARUP Institute for Clinical and Experimental Pathology®

Kushnir MM, Rockwood AL, Nelson GJ, Terry AH, Meikle W. Liquid chromatography-tandem mass spectrometry analysis of urinary free cortisol. Clin Chem. 2003; 49(6 Pt 1): 965-7. PubMed

La'ulu SL, Roberts WL. Performance characteristics of the Architect cortisol immunoassay. Clin Chim Acta. 2008; 388(1-2): 219-21. PubMed

Medical Reviewers

Content Reviewed: 
February 2017

Last Update: July 2017