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Addison's Disease Message Board

Addison's Disease Board Index

You must have the ACTH stimulation to check for addisons.

Diagnostic Testing for Addison's Disease

TEST 1: Electrolyte profile:

OBJECT: To determine if the patient exhibits a normal serum (blood) sodium and potassium levels.

THE TEST: A blood draw followed by automated determination of sodium and potassium levels as well as other standard blood markers.

NORMAL RESULT (will vary somewhat from lab to lab): Sodium 135-150 mEq/L; Potassium 3.5-5.2 mEq/L

PRIMARY ADDISONIAN: Will show significantly below normal values of sodium and a elevated (above normal) levels of potassium.

REASON FOR ABNORMALITY: Low or no production of aldosterone from the adrenal cortex. This steroidal hormone regulates our mineral balance and is called a mineralocorticoid. Primary Addisonians lose sodium and retain potassium. Abnormal values here, in additon to physical signs and symptoms, require the next test.

TEST 2: The ACTH stimulation test:

OBJECT: To determine if the patient's adrenal glands can respond to the ACTH message from the pituitary to increase cortisol production in the adrenal cortex.

THE TEST: The test is usually given first thing in the morning when normal cortisol levels are highest. Blood is withdrawn from the patient to establish a baseline (No instructions regarding necessity for fasting). The patient is given 250 micrograms (ug) of ACTH (Cortrosyn, Cosyntropin, or Synacthen) by injection in saline at one time. Blood is drawn at 30 minutes and/or 60 minutes and the serum cortisol level is determined.

NORMAL RESULTS: Normal pre-injection levels of cortisol are 5-25 ug/dL (138-690 nmol/L). The value should double at 30-60 minutes with a minimum of 20 ug/dL (552 nmol/L). PRIMARY ADDISONIAN: There will be no or little increase in cortisol levels upon ACTH injection. Notes: It is stated in several places that a single test of cortisol levels, or even 24 h urinary levels of cortisol and its metabolites, are NOT DIAGNOSTIC! In the normal individual cortisol levels are seen to pulse. Low cortisol production in either the serum or the urine after ACTH stimulation is diagnostic of Addisons disease.

SECONDARY ADDISONIAN (Pituitary malfunction): Low cortisol production can be seen if the patient has "functional adrenal cortical atrophy" due to prolonged absence of normal ACTH secretion. This type of patient would not show the typical hyper-pigmentation of primary Addisons.

REASON FOR ABNORMALITY: Due to autoimmune, or other destruction of enzymatic (biocatalytic) machinery of the adrenal gland, there is no response to ACTH and no production of cortisol and other adrenal steroids necessary for life. If this test gives normal results and the patient has other signs and symptoms then one of the following tests is required.
Here's what I found on testing for Cushings.

Testing for Cushing’s syndrome is done in two stages. Initial tests are to verify that there is indeed excess cortisol present. These first stage tests include a 24-hour urine test and a single low dose dexamethasone suppression test. The second set of tests are to determine the cause of the increased cortisol: pituitary, adrenal, or other. These tests include a high dose dexamethasone suppression test, a CRH stimulation test, and one or more imaging tests.

Laboratory Tests
Since cortisol levels vary greatly over the course of a day, a single cortisol result is of little value and other ways of measuring overall cortisol production are used.

24-hour Urine Cortisol
24-hour urine cortisol (or urine free cortisol) is often used to evaluate overall cortisol production.

Another approach is to measure cortisol at 11 PM, when normally levels are at their lowest. This can be done on saliva or in the blood. If these tests indicate that cortisol levels are not varying normally and are consistently high, other testing is done to determine the reason for the increased levels.

Dexamethasone Suppression Test
Dexamethasone is a synthetic steroid that mimics cortisol in the feedback inhibition of CRH and ACTH production. There are several versions of the suppression test, which is used to confirm the diagnosis of Cushing’s syndrome. A normal response to dexamethasone is suppression of cortisol secretion. Patients with all types of Cushing’s syndrome will not show adequate suppression after a single low dose of dexamethasone given at bedtime.

Higher doses of dexamethasone can be given over 48 hours to distinguish between an ACTH-producing pituitary tumor and other causes of Cushing’s syndrome.

CRH Stimulation Test
CRH (corticotrophin releasing hormone) is injected and cortisol and ACTH levels are measured at baseline (before CRH) and at 30 and 60 minutes. The normal response is a peak in ACTH levels at 30 minutes with cortisol peaking at 60 minutes. Most patients with Cushing’s syndrome caused by adrenal tumors or ectopic ACTH secreting tumors do not respond to CRH. Frequently, ACTH levels are measured in samples obtained through a catheter placed in the inferior petrosal sinuses, which carry blood from the pituitary glands.

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