Adrenal hypofunction
Adrenal hypofunction: Excerpt from Professional Guide to Diseases (Eighth Edition)
Primary adrenal hypofunction (also called adrenal insufficiency or Addison’s disease) originates within the adrenal gland itself and is characterized by decreased mineralocorticoid, glucocorticoid, and androgen secretion. Adrenal hypofunction can also occur secondary to a disorder outside the gland (such as pituitary tumor, with corticotropin deficiency), but aldosterone secretion frequently continues intact. A relatively uncommon disorder, adrenal hypofunction can occur at any age and in both sexes. Secondary adrenal hypofunction occurs when a patient abruptly stops taking long-term exogenous steroid therapy. With early diagnosis and adequate replacement therapy, the prognosis for adrenal hypofunction is good.
Adrenal crisis (addisonian crisis), a critical deficiency of mineralocorticoids and glucocorticoids, generally follows acute stress, sepsis, trauma, surgery, or omission of steroid therapy in patients who have chronic adrenal insufficiency. A medical emergency, adrenal crisis necessitates immediate, vigorous treatment.
Causes and incidence
Adrenal hypofunction occurs when more than 90% of both adrenal glands are destroyed, an occurrence that typically results from an autoimmune process in which circulating antibodies react specifically against the adrenal tissue. Other causes include tuberculosis (once the chief cause; now responsible for less than 10% of adult cases), bilateral adrenalectomy, hemorrhage into the adrenal gland, neoplasms, and infections (acquired immunodeficiency syndrome, histoplasmosis, and cytomegalovirus). Rarely, a familial tendency to autoimmune disease predisposes the patient to adrenal hypofunction and other endocrinopathies.
Secondary adrenal hypofunction that results in glucocorticoid deficiency can stem from hypopituitarism (causing decreased corticotropin secretion), abrupt withdrawal of long-term corticosteroid therapy (long-term exogenous corticosteroid stimulation suppresses pituitary corticotropin secretion and results in adrenal gland atrophy), or removal of a nonendocrine, corticotropin-secreting tumor. Adrenal crisis follows when trauma, surgery, or other physiologic stress exhausts the body’s stores of glucocorticoids in a person with adrenal hypofunction.
Adrenal hypofunction affects 1 in 16,000 neonates congenitally. In adults, it affects 8 in 100,000 people, and males and females are affected equally. There’s no racial predilection.
Signs and symptoms
Adrenal hypofunction typically produces such effects as weakness, fatigue, weight loss, and various GI disturbances, such as nausea, vomiting, anorexia, and chronic diarrhea. When primary, the disorder usually causes a conspicuous bronze coloration of the skin. The patient appears to be deeply suntanned, especially in the creases of the hands and over the metacarpophalangeal joints, the elbows, and the knees. He may also exhibit a darkening of scars, areas of vitiligo (absence of pigmentation), and increased pigmentation of the mucous membranes, especially the buccal mucosa. Abnormal skin and mucous membrane coloration results from decreased secretion of cortisol (one of the glucocorticoids), which causes the pituitary gland to simultaneously secrete excessive amounts of corticotropin and melanocyte-stimulating hormone (MSH).
Associated cardiovascular abnormalities in adrenal hypofunction include orthostatic hypotension, decreased cardiac size and output, and a weak, irregular pulse. Other clinical effects include decreased tolerance for even minor stress, poor coordination, fasting hypoglycemia (due to decreased gluconeogenesis), and a craving for salty food. Adrenal hypofunction may also retard axillary and pubic hair growth in females, decrease the libido (from decreased androgen production) and, in severe cases, cause amenorrhea.
Secondary adrenal hypofunction produces similar clinical effects but without hyperpigmentation because corticotropin and MSH levels are low. Because aldosterone secretion may continue at fairly normal levels in secondary adrenal hypofunction, this condition doesn’t necessarily cause accompanying hypotension and electrolyte abnormalities.
Alert Adrenal crisis produces profound weakness, fatigue, nausea, vomiting, hypotension, dehydration and, occasionally, high fever followed by hypothermia. If untreated, this condition can ultimately lead to vascular collapse, renal shutdown, coma, and death.
Diagnosis
Diagnosis requires demonstration of decreased corticosteroid concentrations in plasma and an accurate classification of adrenal hypofunction as primary or secondary. If secondary adrenal hypofunction is suspected, the metyrapone test is indicated. This test requires oral or I.V. administration of metyrapone, which blocks cortisol production and should stimulate the release of corticotropin from the hypothalamic-pituitary system. In adrenal hypofunction, the hypothalamic-pituitary system responds normally, and plasma reveals high levels of corticotropin; however, plasma levels of cortisol precursor and urinary concentrations of 17-hydroxycorticosteroids don’t rise.
If either primary or secondary adrenal hypofunction is suspected, a short corticotropin stimulation test may be done. If both corticotropin and cortisol are low, the long corticotropin test may be done. The test involves I.V. administration of corticotropin over 6 to 8 hours, after samples have been obtained to determine baseline plasma cortisol and 24-hour urine cortisol levels. In adrenal hypofunction, plasma and urine cortisol levels fail to rise normally in response to corticotropin; in secondary hypofunction, repeated doses of corticotropin over successive days produce a gradual increase in cortisol levels until normal values are reached.
In a patient with typical addisonian symptoms, the following laboratory findings strongly suggest acute adrenal hypofunction:
❑ decreased cortisol levels in plasma (less than 10 mcg/dl in the morning, with lower levels in the evening); however, this test is time-consuming, and emergency therapy shouldn’t be postponed for test results
❑ decreased serum sodium and fasting blood glucose levels
❑ increased serum potassium and blood urea nitrogen levels
❑ elevated hematocrit and lymphocyte and eosinophil counts
❑ X-rays showing a small heart and adrenal calcification.
Treatment
For all patients with primary or secondary adrenal hypofunction, corticosteroid replacement, usually with cortisone or hydrocortisone (both of which also have a mineralocorticoid effect), is the primary treatment and must continue throughout life. Adrenal hypofunction may also necessitate treatment with I.V. desoxycorticosterone, a pure mineralocorticoid, or oral fludrocortisone, a synthetic mineralocorticoid; both prevent dangerous dehydration and hypotension.
Adrenal crisis requires prompt I.V. bolus administration of hydrocortisone. Later, doses are given I.M. or are diluted with dextrose in saline solution and given I.V. until the patient’s condition stabilizes.
With proper treatment, adrenal crisis usually subsides quickly; the patient’s blood pressure should stabilize, and water and sodium levels should return to normal. After the crisis, maintenance doses of hydrocortisone preserve physiologic stability.
Special considerations
In adrenal crisis, monitor vital signs carefully, especially for hypotension, volume depletion, and other signs of shock (decreased level of consciousness and urine output). Watch for hyperkalemia before treatment and for hypokalemia after treatment (from excessive mineralocorticoid effect).
❑ If the patient also has diabetes, check blood glucose levels periodically because steroid replacement may require adjustment of insulin dosage.
❑ Record weight and intake and output carefully because the patient may have volume depletion. Until onset of mineralocorticoid effect, force fluids to replace excessive fluid loss.
To manage the patient receiving maintenance therapy:
❑ Arrange for a diet that maintains sodium and potassium balances.
❑ If the patient is anorectic, suggest six small meals a day to increase calorie intake. Ask the dietitian to provide a diet high in protein and carbohydrates. Keep a late-morning snack available in case the patient becomes hypoglycemic.
❑ Observe the patient receiving steroids for cushingoid signs such as fluid retention around the eyes and face. Watch for fluid and electrolyte imbalance, especially if the patient is receiving mineralocorticoids. Monitor weight and check blood pressure to assess body fluid status. Remember, steroids administered in the late afternoon or evening may cause stimulation of the central nervous system and insomnia in some patients. Check for petechiae because the patient bruises easily.
❑ If the patient receives glucocorticoids alone, observe for orthostatic hypotension or electrolyte abnormalities, which may indicate a need for mineralocorticoid therapy.
❑ Explain that lifelong steroid therapy is necessary.
❑ Teach the patient the symptoms of too great or too little a dose.
❑ Tell the patient that dosage may need to be increased during times of stress (when he has a cold for example).
❑ Warn that infection, injury, or profuse sweating in hot weather may precipitate adrenal crisis.
❑ Warn the patient that any stress may necessitate additional cortisone to prevent adrenal crisis.
❑ Instruct the patient to always carry a medical identification card stating that he takes a steroid and giving the name of the drug and the dosage.
❑ Tell the patient to keep an emergency kit available containing hydrocortisone in a prepared syringe for use in times of stress.
❑ Teach the patient how to give himself an injection of hydrocortisone.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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