Cushing's syndrome laboratory findings

Cushing's syndrome Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Cushing's syndrome from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Laboratory Findings
Electrocardiogram
Chest X Ray
CT
MRI
Echocardiography or Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Cushing's syndrome laboratory findings On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Cushing's syndrome laboratory findings All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Cushing's syndrome laboratory findings
CDC on Cushing's syndrome laboratory findings
Cushing's syndrome laboratory findings in the news
Blogs on Cushing's syndrome laboratory findings
Directions to Hospitals Treating Cushing's syndrome
Risk calculators and risk factors for Cushing's syndrome laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Furqan M M. M.B.B.S[2]

Overview

When Cushing's is suspected, either a dexamethasone suppression test (administration of dexamethasone and frequent determination of cortisol and ACTH level), or a 24-hour urinary measurement for cortisol offer equal detection rates. Dexamethasone is a glucocorticoid and simulates the effects of cortisol, including negative feedback on the pituitary gland. When dexamethasone is administered and a blood sample is tested, high cortisol would be indicative of Cushing's syndrome. A novel approach, recently cleared by the US FDA, is sampling cortisol in saliva over 24 hours, which may be equally sensitive, as late night levels of salivary cortisol are high in Cushingoid patients. Other pituitary hormone levels may need to be ascertained.

Laboratory Findings

Diagnosis of hyercortisolism

Hypercortisolism can be established by any of the following tests:

• 24 hr urine cortisol
• Midnight salivary cortisol
• Low dose dexamethasone suppression test; high cortisol level after the dexamethasone test is suggestive of hypercortisolism.

Tests to establish the cause of hypercortisolism

• Measure Adrenocorticotrophic hormone (ACTH) levels.
• If ACTH is less than 5 pg/dl, perform an adrenal CT scan or MRI to search for possible adrenal causes.
• If ACTH is higher than 5 pg/dl Corticotrophic releasing hormone (CRH) test also called desmopressin test can be used to differentiate between cushing disease and ectopic ACTH secretion.

24 hr urine cortisol or midnight salivary cortisol shows hypercortisolism

Measure serum ACTH

<5pg/ml

5-20pg/dl

>20pg/dl

ACTH independent Cushing syndrome

CRH (desmopressin) test

ACTH dependent Cushing syndrome

Adrenal CT/MRI

Evaluate as ACTH independent Cushing syndrome if NO ACTH response

Evaluate as ACTH dependent Cushing syndrome if there is an ACTH response

CRH (desmopressin) AND high dose dexamethasone suppression test

Adequate stimulation and suppression

Mixed or negative response

Cushing disease

Inferior petrosal sinus sampling

Cushing disease if step-up in ACTH

Ectopic ACTH secretion if no step-up in ACTH

References

Template:WH Template:WS