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Adrenal insufficiency is a state of inadequate cortisol production caused by a problem in the hypothalamic-pituitary-adrenal axis. It can be primary, like Addison's disease (a problem with the adrenal glands themselves), or secondary (as when the anterior pituitary fails to release adrenocorticotropic hormone [ACTH] or the hypothalamus doesn't produce corticotropin-releasing hormone [CRH] to stimulate ACTH release from the pituitary). Healthy adrenal glands require ACTH stimulation to release cortisol into the blood.
An ACTH stimulation blood test is ordered to evaluate whether the adrenal glands are producing sufficient amounts of cortisol. If your patient's adrenal glands are normal, administering synthetic ACTH should raise his serum cortisol level. But if the adrenal glands are dysfunctional, they won't respond to the administered ACTH, and his serum cortisol levels won't rise.
Assessing for adrenal insufficiency. Cortisol plays many roles in the body, so a deficiency causes various signs and symptoms. Your patient may have fatigue, weight loss, anorexia, nausea, vomiting, diarrhea, dehydration, abdominal pain, fever, mental status changes, muscle weakness, and hypotension that doesn't respond to fluid challenges or vasopressors such as dopamine. Lab abnormalities may include hyponatremia, hyperkalemia, hypoglycemia, metabolic acidosis, and eosinophilia.
Performing the test. An ACTH stimulation test is usually started at 8:00 a.m., when the patient is fasting and blood cortisol levels are typically highest, so keep him N.P.O. after midnight. For a critically ill patient, facility protocol may permit doing the test at any time because critical illness typically stresses the adrenal glands, keeping cortisol levels constant throughout the day. A baseline blood cortisol level and blood cortisol levels drawn 30 and 60 minutes after synthetic ACTH administration are obtained following facility protocol.
What do the results mean? Normal cortisol values vary among labs. Most labs define "normal" as 18 to 25 mcg/dl, but a normal value can be as low as 16 mcg/dl if ACTH was administered I.M. All three results below normal signal adrenal insufficiency. At least one cortisol value must be within or above the normal range to rule out the problem.
If your patient's adrenals are producing normal amounts of cortisol, a CRH test may be ordered to determine if his pituitary or hypothalamus is causing his problems.
What can affect the results? Taking estrogen, exogenous steroids, amphetamines, or alcohol can increase a patient's cortisol levels. Other factors that can influence results include stress, physical activity, collecting blood in the wrong type of tube (plastic is generally required), and taking specimens at different times of day.
What care does the patient require? All patients with primary or secondary adrenal insufficiency should receive exogenous steroid replacement. Hydrocortisone I.V. or oral prednisone is typically administered to simulate diurnal adrenal rhythm, with two-thirds of the dose given in the morning and one-third in the afternoon. When a critically ill patient has signs and symptoms of adrenal insufficiency but his cortisol levels are within the low-normal range, the practitioner may order a trial treatment with exogenous glucocorticoids.
1. Fischbach FT. A Manual of Laboratory and Diagnostic Tests. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004.
2. Kee JL. Laboratory and Diagnostic Tests with Nursing Implications. 6th ed. Upper Saddle River, NJ: Pearson Education, Inc.; 2002.
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