What lab test for adrenal insufficiency
What lab test for adrenal insufficiency Adrenal insufficiency, also known as Addison’s disease or secondary adrenal failure, occurs when the adrenal glands do not produce enough of the hormones cortisol and, in some cases, aldosterone. Detecting this condition accurately is crucial because symptoms can be subtle, nonspecific, and easily mistaken for other illnesses. Laboratory testing plays an essential role in confirming the diagnosis, assessing the severity, and guiding appropriate treatment.
The initial step in evaluating suspected adrenal insufficiency often involves measuring serum cortisol levels. A random serum cortisol test, taken at any time of the day, can provide a preliminary indication. However, since cortisol follows a diurnal rhythm—peaking in the early morning and declining throughout the day—morning cortisol levels are more informative. A low morning serum cortisol level, especially below 3 mcg/dL (83 nmol/L), strongly suggests adrenal insufficiency, prompting further testing to confirm the diagnosis. What lab test for adrenal insufficiency
To improve diagnostic accuracy, an adrenocorticotropic hormone (ACTH) stimulation test is frequently employed. This test assesses the adrenal glands’ ability to produce cortisol in response to synthetic ACTH, a hormone that stimulates cortisol secretion. The most common version is the high-dose (250 mcg) ACTH stimulation test. In this procedure, blood samples are taken before and after administering synthetic ACTH, typically at 30 and 60 minutes. In healthy individuals, cortisol levels should rise significantly—usually by at least 18–20 mcg/dL (500–550 nmol/L)—indicating proper adrenal function. A blunted or absent response suggests adrenal insufficiency. What lab test for adrenal insufficiency
What lab test for adrenal insufficiency In cases where secondary adrenal insufficiency is suspected—due to pituitary or hypothalamic causes—additional tests may be warranted. The insulin tolerance test (ITT) is considered the gold standard for diagnosing secondary adrenal insufficiency because it assesses the entire hypothalamic-pituitary-adrenal (HPA) axis. In this test, insulin is administered to induce hypoglycemia, which should normally stimulate cortisol and ACTH release. However, due to its risks, this test is performed under strict medical supervision.
Measurement of plasma ACTH levels can further distinguish between primary and secondary adrenal insufficiency. Elevated ACTH levels typically indicate primary adrenal failure, where the problem originates in the adrenal glands themselves. Conversely, low or inappropriately normal ACTH levels suggest secondary or tertiary adrenal insufficiency, stemming from pituitary or hypothalamic dysfunction.
Additional laboratory assessments include serum electrolytes, particularly sodium and potassium, since aldosterone deficiency in primary adrenal insufficiency can lead to hyponatremia and hyperkalemia. Imaging studies, such as CT scans of the adrenal glands or pituitary, may complement lab findings by identifying structural abnormalities. What lab test for adrenal insufficiency
In summary, diagnosing adrenal insufficiency involves a combination of hormone measurements and dynamic testing. Morning serum cortisol levels serve as a useful screening tool, while ACTH stimulation tests provide definitive evidence of adrenal function. Accurate interpretation of these tests, along with clinical correlation, is essential for proper diagnosis and management. What lab test for adrenal insufficiency
