Dexamethasone suppression test

Dexamethasone suppression test
Diagnostics
Dexamethasone
OPS-301 code	1-797

proopiomelanocortin derivatives
POMC
γ-MSH	ACTH		β-lipotropin
	α-MSH	CLIP	γ-lipotropin		β-endorphin
				β-MSH

The dexamethasone suppression test is designed to diagnose and differentiate among the various types of Cushing's syndrome and other hypercortisol states.^[1]

It has also been used in the research of depression.^[2]

Physiology

Dexamethasone is an exogenous steroid that provides negative feedback to the pituitary to suppress the secretion of ACTH. This steroid is unable to pass the blood brain barrier which allows this test to assess a specific part of the hypothalamic-pituitary-adrenal axis. Specifically, dexamethasone binds to glucocorticoid receptors in the pituitary gland, which lies outside the blood brain barrier, resulting in regulatory modulation.^[3]

Interpretation

Low-dose and high-dose variations of the test exist.^[4]

The test is given at low (usually 1–2 mg) and high (8 mg) doses of dexamethasone and the levels of cortisol are measured to obtain the results.^[1]

A low dose dexamethasone suppresses cortisol in individuals with no pathology in endogenous cortisol production. A high dose dexamethasone exerts negative retro-control on pituitary ACTH producing cells but not on ectopic ACTH producing cells or adrenal adenoma.

Low-dose

A normal result is decrease in cortisol levels upon administration of low-dose dexamethasone. Results indicative of Cushing's disease involve no change in cortisol on low-dose dexamethasone, but inhibition of cortisol on high-dose dexamethasone. If the cortisol levels are unchanged by low- and high-dose dexamethasone then other causes of Cushing's syndrome must be considered with further work-up necessary.

High-dose

After the high-dose dexamethasone, it may be possible to make further interpretations.^[5]

ACTH	Cortisol	Interpretation
undetectable or low	is not suppressed by high or low doses.	Primary Adrenal Cushing syndrome is likely.
normal to elevated	is not suppressed by low or high doses	Ectopic ACTH syndrome is likely. If an adrenal tumor is not apparent, a chest CT and abdominal CT is indicated to rule out a different tumor secreting ACTH.
elevated	is not suppressed by low doses, but is suppressed by high doses	Cushing's disease should be considered. A pituitary MRI would be needed to confirm.

Equivocal results should be followed by a CRH stimulation test, with inferior petrosal sinus sampling.

References

1. ^ ^{a b} Medline Plus "Dexamethasone suppression test"
2. ^ Fountoulakis KN, Gonda X, Rihmer Z, Fokas C, Iacovides A (2008). "Revisiting the Dexamethasone Suppression Test in unipolar major depression: an exploratory study". Ann Gen Psychiatry 7: 22. doi:10.1186/1744-859X-7-22. PMC 2590593. PMID 19014558. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2590593. 
3. ^ Cole MA, Kim PJ, Kalman BA, Spencer RL (February 2000). "Dexamethasone suppression of corticosteroid secretion: evaluation of the site of action by receptor measures and functional studies". Psychoneuroendocrinology 25 (2): 151–67. doi:10.1016/S0306-4530(99)00045-1. PMID 10674279. http://linkinghub.elsevier.com/retrieve/pii/S0306-4530(99)00045-1. 
4. ^ Isidori AM, Kaltsas GA, Mohammed S, et al (November 2003). "Discriminatory value of the low-dose dexamethasone suppression test in establishing the diagnosis and differential diagnosis of Cushing's syndrome". J. Clin. Endocrinol. Metab. 88 (11): 5299–306. doi:10.1210/jc.2003-030510. PMID 14602765. http://jcem.endojournals.org/cgi/pmidlookup?view=long&pmid=14602765. 
5. ^ Kumar, Abbas, Fausto. Robbins and Cotran Pathologic Basis of Disease, 7th ed. Elsevier-Saunders; New York, 2005

This article related to pathology is a stub. You can help Wikipedia by expanding it.v · Categories: Endocrine procedures Pathology stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем написать реферат John Tate (disambiguation) Pullman loaf Look at other dictionaries: dexamethasone suppression test high-dose — (for Cushing syndrome) urinary levels of cortisol and 17 hydroxycorticosteroid are measured following administration of dexamethasone at 16 times the level used in replacement therapy; cortisol secretion is suppressed in patients with Cushing… …   Medical dictionary dexamethasone suppression test low-dose — (for Cushing syndrome) urinary levels of cortisol and 17 hydroxycorticosteroid are measured following administration of dexamethasone at three to four times the level used in replacement therapy; cortisol secretion is suppressed in normal… …   Medical dictionary Dexamethasone — Systematic (IUPAC) name (8S,9R …   Wikipedia dexamethasone — A potent synthetic analogue of cortisol, with similar biological action; used as an anti inflammatory agent and as a test material for adrenal cortical function. * * * dexa·meth·a·sone .dek sə meth ə .s …   Medical dictionary test — 1. To prove; to try a substance; to determine the chemical nature of a substance by means of reagents. 2. A method of examination, as to determine the presence or absence of a definite disease or of some substance in any of the fluids, tissues,… …   Medical dictionary ACTH stimulation test — Diagnostics OPS 301 code 1 797 The ACTH stimulation test (also called the cosyntropin test, tetracosactide test or Synacthen test) is a medical test usually ordered and interpreted by endocrinologists to assess the functioning of the …   Wikipedia Glucose tolerance test — Intervention MeSH D005951 A glucose tolerance test is a medical test in which glucose is given and blood samples taken afterward to determine how quickly it is cleared from the blood …   Wikipedia Incidentaloma — In medicine, an incidentaloma is a tumor ( oma ) found by coincidence ( incidental ) without clinical symptoms or suspicion. It is a common problem: up to 7% of all patients over 60 may harbor a benign growth, often of the adrenal gland, which is …   Wikipedia Cushing's disease — Classification and external resources ICD 10 E24.0 Cushing s disease is a cause of Cushing s Syndrome characterised by increased secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary. This is most often as a result of a… …   Wikipedia Cushing's syndrome — Classification and external resources ICD 10 E24 ICD 9 255.0 …   Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”