Addison's disease laboratory findings
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Diagnosis of Addison's disease is made by routine blood tests and specific tests. ACTH stimulation test is a specific test employed to determine the function of adrenal glands and to diagnose Addison's disease. The prominent finding of a rapid ACTH stimulation test includes failure of cortisol to rise in response to ACTH injection. Other routine laboratory tests employed include plasma cortisol level, serum ACTH level, plasma renin activity, aldosterone levels and serum biochemistry.
- Specific tests to determine the function of adrenal glands include:
- Routine blood tests
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Specific tests to determine adrenal gland function
ACTH Stimulation Test (Rapid ACTH Stimulation Test)
- This is the most specific test for diagnosing Addison's disease.
- In this test, blood cortisol, urine cortisol, or both are measured before and after a synthetic form of ACTH is given by injection.
- It is called short, or rapid ACTH test because measurement of cortisol in blood is repeated 30 to 60 minutes after an intravenous ACTH injection.
- 250 µg synthetic ACTH (cosyntropin) is administered intravenously or intramuscularly.
- The normal response after an injection of ACTH is a rise in blood and urine cortisol levels.
- Those with primary adrenal insufficiency fail to increase cortisol levels above 18 µg/dL; those with secondary or tertiary adrenal insufficiency also fail to achieve cortisol levels above 18 µg/dL as long as their condition has been present long enough to allow adrenal atrophy (about 2-4 weeks).
- If a subnormal cortisol response occurs, ACTH measurement and other tests should distinguish between primary and secondary and tertiary causes
- Patients with either form of adrenal insufficiency respond poorly or do not respond at all.
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cosyntropin stimulation test
|Adrenal insufficiency is ruled out|
|Adrenal insufficiency confirmed|
CRH Stimulation Test
- When the response to the short ACTH test is abnormal, a "long" CRH stimulation test is required to determine the cause of adrenal insufficiency.
- In this test, 1 μg synthetic CRH is injected intravenously and blood cortisol is measured before and 30, 60, 90, and 120 minutes after the injection.
- There is some evidence that the low-dose ACTH test is more sensitive than the standard 250 μg test in identifying partial or mild cases of secondary or tertiary adrenal insufficiency
- Patients with primary adrenal insufficiency have high ACTHs but do not produce cortisol.
- Patients with secondary adrenal insufficiency have deficient cortisol responses but absent or delayed ACTH responses.
- Absent ACTH response points to the pituitary as the cause; a delayed ACTH response points to the hypothalamus as the cause.
Routine investigations include
- Plasma cortisol level
- Serum ACTH level
- Plasma renin activity and aldosterone levels
- Serum biochemistry
|Test||Advantage||Normal values||Laboratory Finding|
|Serum ACTH level||
|Plasma renin activity and aldosterone levels||
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- Chakera AJ, Vaidya B (2010). "Addison disease in adults: diagnosis and management". Am. J. Med. 123 (5): 409–13. doi:10.1016/j.amjmed.2009.12.017. PMID 20399314.
- Husebye ES, Allolio B, Arlt W, Badenhoop K, Bensing S, Betterle C, Falorni A, Gan EH, Hulting AL, Kasperlik-Zaluska A, Kämpe O, Løvås K, Meyer G, Pearce SH (2014). "Consensus statement on the diagnosis, treatment and follow-up of patients with primary adrenal insufficiency". J. Intern. Med. 275 (2): 104–15. doi:10.1111/joim.12162. PMID 24330030.
- Puttanna A, Cunningham AR, Dainty P (2013). "Addison's disease and its associations". BMJ Case Rep. 2013. doi:10.1136/bcr-2013-010473. PMC 3736622. PMID 23893277.