Adrenal insufficiency can be difficult to diagnose. Your doctor will begin by asking about your medical history and about any obvious symptoms you are experiencing. Tests that measure the levels of cortisol and aldosterone are used to make a definite diagnosis and include the following:
ACTH Stimulation Test: This is the most specific test for diagnosing adrenal insufficiency. Blood cortisol levels are measured before and after a synthetic form of adrenocorticotrophic hormone (ACTH), a hormone secreted from the anterior pituitary, is given by injection.
Insulin-Induced Hypoglycemia Test: The insulin-induced hypoglycemia test is used to determine how the hypothalamus, pituitary and adrenal glands respond to stress. During this test, blood is drawn to measure the blood glucose and cortisol levels, followed by an injection of fast-acting insulin. Blood glucose and cortisol levels are measured again 30, 45 and 90 minutes after the insulin injection. The normal response is for blood glucose levels to fall (this represents the stress) and cortisol levels to rise.
Once a diagnosis of adrenal insufficiency has been made, a computed tomography (CT) scan of the abdomen may be taken to see if the adrenal glands are diminished in size, reflecting destruction, or enlarged, reflecting infiltration by some independent disease process. The scan also may show signs of calcium deposits, which may indicate previous exposure to tuberculosis. A tuberculin skin test may be used to address the latter possibility.
A number of imaging tools may be used to examine the size and shape of the pituitary gland. The most common is the magnetic resonance imaging (MRI) scan, which produces a series of images that provide a cross-sectional picture of the pituitary and the area of the brain that surrounds it.
In addition, the function of the pituitary and its ability to produce other hormones are tested. Typically, measurements of ACTH — the pituitary hormone most relevant for maintenance of normal adrenal function — along with thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), luteinizing hormone (LH) and prolactin are made under resting conditions and following provocative simulation, such as following the administration of corticotrophin releasing hormone (CRH), which leads to an increase in ACTH levels under normal conditions.
Reviewed by health care specialists at UCSF Medical Center.