Sometimes, deficiency of the adrenal gland can cause an insidious and gradually severe fatigue. There are two tests that can be done to check for this. The simplest test is called a cosyntropin (Cortrosyn) stimulation test. Cosyntropin is a drug that is similar to ACTH (adrenocorticotropic hormone), a hormone made by the pituitary gland to stimulate the adrenal gland, much like TSH stimulates the thyroid gland. To do this test, your physician obtains a blood test for cortisol, then gives you an injection of cosyntropin. Your cortisol level is checked after thirty minutes, and then after another thirty minutes (an hour in total). Normal adrenal glands will be able to produce a cortisol level greater than 20 after the cosyntropin injection. If the cortisol level does not rise sufficiently, then it may be necessary to take cortisol replacement therapy for life.
Three different steroid drugs can be used for cortisol replacement therapy, the two best being hydrocortisone and cortisone acetate. They are given as a pill in the morning and half of this dose in the evening. An alternative drug, prednisone, is sometimes used as a single pill each morning. If both adrenal glands are not working at all, then it may be necessary to take an additional medication to provide another type of steroid hormone, known as a mineralocorticoid, to keep the blood pressure from getting too low.
Sometimes, the cosyntropin stimulation test may not be accurate if there is pituitary or hypothalamic disease as the cause of low adrenal function. Two other tests that work better for this situation are the metyrapone suppression test and insulin-hypoglycemia test. Detailed discussions of these tests are beyond the scope of this book, but they should be well known to the endocrinologists who administer them.
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