How Is Adrenal Insufficiency Diagnosed?
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Definition
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The adrenal glands are a highly vascularized pair of glands located on the tops of the kidneys. They contain two parts: the adrenal medulla and the adrenal cortex. The adrenal medulla is the inner part of the adrenal gland, while the adrenal cortex is the outside portion of the gland. The adrenal medulla produces epinephrine and norepinephrine. The adrenal cortex produces steroid hormones, such as testosterone, cortisone and aldosterone. Adrenal insufficiency occurs when the adrenal glands no longer produce the necessary amount of hormones. Adrenal insufficiency can be primary, also known as Addison's disease, or secondary.
Primary Adrenal Insufficiency
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Primary adrenal insufficiency, Addison's disease, can affect any sex or age. One to four out of every 100,000 people is affected. With Addison's disease, the adrenal glands do not produce enough cortisol and often aldosterone. Cortisol has many important functions in the body, including maintaining glucose levels, regulating the metabolism and maintaining blood pressure. Aldosterone also helps maintain blood pressure, in addition to the salt and water balance in the body. Symptoms of Addison's disease are weight loss, muscle weakness, low blood pressure, appetite loss, worsening fatigue and hyperpigmentation of the skin. Addison's disease is most often caused by autoimmune disorders or tuberculosis. It may also be caused by chronic infection, AIDS, bleeding into the adrenal glands, cancer or genetic defects.
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Secondary Adrenal Insufficiency
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The pituitary gland, which is located in the brain, produces a hormone called adrenocorticotropin (ACTH). ACTH stimulates the adrenal gland to produce cortisol. If the pituitary gland is not producing enough ACTH, the adrenal glands, in turn, do not produce enough cortisol. This is called secondary adrenal insufficiency. The symptoms are the same as Addison's disease, with the exception of hyperpigmentation of the skin, which does not occur in secondary adrenal insufficiency. Aldosterone production is not usually altered in secondary adrenal insufficiency. Removal of tumors in or the entire pituitary gland, radiation treatment to the pituitary gland or bleeding in the pituitary gland may cause secondary adrenal insufficiency. Another cause is when someone stops taking glucocorticoid medications, although this would only be temporary.
Diagnosis
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It may be difficult to diagnose adrenal insufficiency in the early stages. Doctors may suspect it based on the symptoms and medical history of the patient. When suspected, the doctor will order laboratory tests, which can confirm his suspicions. The most common test used is the ACTH stimulation test. This test is done using blood, urine or both. The cortisol levels are measured, and then a synthetic form of ACTH is administered by injection. The cortisol levels are measured again after the injection. If a person has adrenal insufficiency, his cortisol levels will not increase much after the ACTH injection.
If the ACTH test shows abnormal results, the CRH (corticotropin-releasing hormone) stimulation test may be performed. In this test, the cause of adrenal insufficiency can possibly be determined. Synthetic CRH is injected into the patient, and the cortisol levels in the blood are then measures at 30, 60, 90 and 120 minutes following the injection. People who have Addison's disease will produce high levels of ACTH, but not cortisol. Those with secondary adrenal insufficiency will have delayed ACTH or no ACTH responses. Delayed ACTH responses indicate a pituitary problem. No ACTH responses indicate a problem with the hypothalamus.
If Addison's disease has been diagnosed, additional tests such as X-rays or ultrasounds of the abdomen may be performed. These tests are going to look for calcium deposits on the adrenal glands, which may indicate tuberculosis or bleeding. Blood tests can be done to detect autoimmune disorders. If secondary adrenal insufficiency has been diagnosed, a computerized tomography (CT) scan or a magnetic resonance imaging (MRI) scan may be ordered to look at the pituitary gland. Blood work is also done to assess the other hormones produced by the pituitary gland.
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