Adrenal insufficiency

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CHAPTER 30

Adrenal insufficiency

1. What is adrenal insufficiency, and how is it categorized?

2. What are common causes of adrenal insufficiency?

Autoimmune adrenalitis (Addison’s disease) is the most common cause of primary adrenal insufficiency and is associated with increased levels of 21-hydroxylase antibodies. Addison’s disease can occur in isolation or in combination with other endocrine deficiencies as part of an autoimmune polyglandular syndrome. The most common cause of central (secondary/tertiary) adrenal insufficiency is withdrawal of glucocorticoids after long-term use. Central adrenal insufficiency can also occur as part of panhypopituitarism from large pituitary tumors or their treatment with surgery and/or radiation therapy. See Table 30-1 for other causes of adrenal insufficiency.

TABLE 30-1.

CAUSES OF ADRENAL INSUFFICIENCY

Primary Autoimmune
  Bilateral adrenal hemorrhage or thrombosis: coagulopathy, meningococcal sepsis
  Metastases: lymphoma, lung, breast, renal, gastrointestinal
  Infectious: tuberculosis, human immunodeficiency virus, cytomegalovirus, fungal (Histoplasma, Coccidioides)
  Adrenoleukodystrophy and other congenital disorders
  After adrenalectomy
  Infiltrative: hemochromatosis, amyloidosis
  Congenital adrenal hyperplasia
  Adrenal enzyme deficiency
  Drugs (see text)
Secondary Withdrawal of long-term suppressive glucocorticoid therapy
  Pituitary tumors including craniopharyngioma
  Metastases to the pituitary
  Pituitary surgery or irradiation
  Lymphocytic hypophysitis
  Infiltrative diseases: hemochromatosis, sarcoidosis, histiocytosis X
  Infection (e.g., tuberculosis, histoplasmosis)
  Sheehan syndrome (massive blood loss leading to shock in the peripartum period)
  Severe head trauma disrupting the pituitary stalk or otherwise affecting the pituitary
Tertiary Withdrawal of long-term suppressive glucocorticoid therapy
  Hypothalamic tumors
  Metastases to the hypothalamus
  Infiltrative diseases affecting the hypothalamus
  Cranial irradiation
  Trauma
  Infections (e.g., tuberculosis)

3. What are common symptoms of adrenal insufficiency?

4. How does adrenal insufficiency usually present?

5. What laboratory abnormalities can be found in adrenal insufficiency?

The classic laboratory abnormalities are hyponatremia and hyperkalemia. The hyperkalemia is due to mineralocorticoid deficiency, whereas the hyponatremia occurs mainly because of glucocorticoid deficiency. Hyponatremia is the result of elevated vasopressin values with free water retention, shift of extracellular sodium into cells, and decreased delivery of filtrate to the diluting segments of the nephron due to decreased glomerular filtration rate. Azotemia can be seen because of hypovolemia. Patients often demonstrate a normocytic normochromic anemia and may have eosinophilia and lymphocytosis. Mild to moderate hypercalcemia may occur. Fasting blood glucose is usually low-normal, but occasionally patients can have fasting or postprandial hypoglycemia. Patients with coexisting type 1 diabetes mellitus and adrenal insufficiency may experience greater frequency and severity of hypoglycemic episodes.

6. How do the clinical presentations of primary and central forms of adrenal insufficiency differ?

7. How is adrenal insufficiency usually diagnosed biochemically?

In the outpatient setting, a low morning cortisol value (< 3 μg/dL) is sufficient to diagnose adrenal insufficiency, and a high morning cortisol value (> 20 μg/dL) excludes the diagnosis. In most instances, a dynamic test, the cosyntropin stimulation test, is also performed. This test determines whether the adrenals are able to respond to maximal stimulation by synthetic ACTH. This test can also be used in the diagnosis of central adrenal insufficiency, as long as sufficient time has elapsed for the adrenal cortex to atrophy in response to lack of ACTH stimulation.

The standard cosyntropin test is performed by collecting a specimen for measurement of a baseline serum cortisol level, administration of 250 μg of cosyntropin (brand name Cortrosyn, Synacthen) intravenously (IV) or intramuscularly (IM), and then collecting specimens for serum cortisol measurement 30 and 60 minutes later. An abnormal result is defined as a stimulated cortisol level at either 30 or 60 minutes of less than 18 to 20 μg/dL (< 450-500 nmol/L). This test can be performed at any time during the day. If an individual is receiving glucocorticoid therapy, the dose should be withheld (12 hours for hydrocortisone, 24 hours for prednisone) before the test is performed to avoid detection of synthetic glucocorticoids in the cortisol assay.

Other dynamic testing includes the insulin tolerance test, metyrapone test, glucagon stimulation test, and CRH stimulation test. The insulin tolerance test evaluates the hypothalamic-pituitary-adrenal (HPA) axis in response to insulin-induced hypoglycemia (blood glucose level < 40 mg/dL). This test should be performed in experienced centers only by trained staff, and should not be performed if the individual has significant coronary artery disease or an uncontrolled seizure disorder.

8. What about the low-dose cosyntropin stimulation test?

It has been argued that mild cases of primary adrenal insufficiency may be missed with the standard-dose cosyntropin stimulation test because the dose of ACTH administered in this test is quite supraphysiologic. Data from studies examining the potential role of low-dose cosyntropin stimulation testing, in which 1 μg cosyntropin is administered, do not clearly establish that the low-dose test is better than the standard test. There are several potential problems with performing the test, including false-positive results because of inaccurate or irreproducible dilution of cosyntropin, the need for IV administration, and the need for carefully timed sampling for serum cortisol levels. It is unclear whether abnormal results from this test are clinically relevant. Therefore the standard-dose test should be used in most instances.

9. What testing can be used to distinguish primary from central adrenal insufficiency?

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