II. Background

  1. Two stage testing described below will miss cases
  2. The low dose (1 mg) test is not adequately sensitive

III. Indications: Cushing's Disease Screening

  1. Second line test
  2. Start with 24-hour Urinary free cortisol level

IV. Mechanism

  1. Test measures Adrenal Gland response to ACTH
  2. ACTH should decrease in response to Dexamethasone
  3. Decreased ACTH should result in decreased Cortisol
  4. Failure for Cortisol to suppress suggests 2 causes
    1. Pituitary GlandACTH over-produced or
    2. Adrenal GlandCortisol over-produced

V. Protocol

  1. Step 1: Draw Serum Cortisol at 4 pm on day 1
  2. Step 2: Patient takes Dexamethasone 1 mg at 11 pm day 1
  3. Step 3: Draw Serum Cortisol at 8-9 am on day 2

VI. Interpretation (Based on Serum Cortisol on day 2, 8 am)

  1. AM Serum Cortisol <5 mcg/dl (especially if <1.8 mcg/dl)
    1. Normal response (Suppresses)
  2. AM Serum Cortisol >5 mcg/dl
    1. Cushing's Disease
    2. Repeating with Dexamethasone 8 mg determines site
      1. Adrenal Gland source will not suppress
      2. Pituitary source will suppress

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Related Studies

Ontology: Dexamethasone suppression test (C0430115)

Definition (PSY) Laboratory analysis of hypersecretion of cortisol and the body's failure to suppress cortisol after the administration of dexamethasone. Used primarily for diagnosis of major depressive disorders.
Definition (CSP) injection of dexamethasone causes serum cortisol to fall; this can be correlated with behavioral measures of depression, but the test is not reliable enough for diagnostic use.
Concepts Laboratory Procedure (T059)
SnomedCT 392884002, 393839005, 252190006
Italian Test di soppressione con desametasone
English Dexamethasone suppression test, DST, dexamethasone suppression test, dexamethasone suppression tests, dst, Dexamethasone suppression test (procedure), Dexamethasone Suppression Test
Czech Dexametazonový supresní test
Hungarian Dexamethason suppressziós vizsgálat
Japanese デキサメタゾン抑制試験, デキサメタゾンヨクセイシケン
Spanish prueba de supresión con dexametasona (procedimiento), prueba de supresión con dexametasona, Prueba de supresión con dexametasona
Portuguese Exame de supressão de dexametasona
Dutch dexamethason-suppressietest
French Épreuve de freinage à la dexaméthasone
German Dexamethason-Suppressionstest

Ontology: Low dose dexamethasone suppression test (C0430116)

Concepts Laboratory Procedure (T059)
SnomedCT 252191005
English Dexamethasone Test Low Dose Suppression, Low dose dexameth supp test, Low dose dexamethasone suppression test, Low dose dexamethasone suppression test (procedure)
Spanish prueba de Liddle a dosis bajas, prueba de supresión con dexametasona a dosis bajas (procedimiento), prueba de supresión con dexametasona a dosis bajas