Adrenal hypofunction
Adrenal hypofunction: Excerpt from Handbook of Diseases
Primary adrenal hypofunction or insufficiency (Addison’s disease) originates within the adrenal gland itself and is characterized by decreased mineralocorticoid, glucocorticoid, and androgen secretion. Secondary adrenal hypofunction is due to impaired pituitary secretion of corticotropin and is characterized by decreased glucocorticoid secretion. Secretion of aldosterone, the major mineralocorticoid, is often unaffected.
Addison’s disease is relatively uncommon, though it can occur at any age, in either sex. Secondary adrenal hypofunction occurs when a patient abruptly stops taking an exogenous steroid after long-term therapy or when the pituitary is injured by a tumor or by infiltrative or autoimmune processes. With an early diagnosis and adequate replacement therapy, the prognosis for the person with 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
The following are causes of primary and secondary adrenal hypofunction and adrenal crisis.
Primary hypofunction
Addison’s disease occurs when more than 90% of both adrenal glands are destroyed. Such destruction usually results from an autoimmune process (autoimmune adrenalitis) in which circulating antibodies react specifically against the adrenal tissue.
CLINICAL TIP: Suspect adrenal insufficiency in patients with acquired immunodeficiency syndrome. Although symptoms may not be present, testing frequently reveals abnormal results.
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 (histoplasmosis, cytomegalovirus). Rarely, a family history of autoimmune disease predisposes the patient to Addison’s disease and other endocrinopathies.
Secondary hypofunction
Secondary hypofunction, which 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 the removal of a corticotropin-secreting tumor.
Adrenal crisis
After trauma, surgery, or other physiologic stress, adrenal crisis exhausts the body’s stores of glucocorticoids in a person with adrenal hypofunction.
Signs and symptoms
Signs and symptoms vary with the type of adrenal hypofunction.
Primary hypofunction
Addison’s disease typically produces weakness, fatigue, weight loss, nausea, vomiting, and anorexia. Asthenia (constant fatigue) is the cardinal symptom, most evident in times of stress.
The disorder also 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 also may exhibit a darkening of scars, areas of vitiligo (absence of pigmentation), and increased pigmentation of the mucous membranes, especially the buccal mucosa. Such abnormal skin and mucous membrane coloration results from decreased secretion of cortisol (a glucocorticoid), which causes the pituitary gland to simultaneously secrete excessive amounts of corticotropin and melanocyte-stimulating hormone (MSH).
Associated cardiovascular abnormalities include orthostatic hypotension, decreased cardiac size and output, and a weak, irregular pulse.
Other signs and symptoms include decreased tolerance for even minor stress, fasting hypoglycemia (due to decreased gluconeogenesis), and a craving for salty food due to decreased mineralocorticoid secretion, which normally causes salt retention.
GENDER INFLUENCE: In women with adrenal hypofunction, androgen levels are low, though they may be treated with daily replacement of 25 to 50 mg of dehydroepiandrosterone to improve quality of life and skeletal density. Also, axillary and pubic hair may be decreased due to loss of adrenal androgens.
Secondary hypofunction
Secondary hypofunction produces signs and symptoms similar to those of primary hypofunction but without hyperpigmentation because corticotropin and MSH levels are low. Because aldosterone secretion may continue at fairly normal levels in those with secondary adrenal hypofunction, this condition doesn’t necessarily cause accompanying hypotension and electrolyte abnormalities.
Adrenal crisis
Besides producing profound weakness, adrenal crisis also causes 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
The diagnosis of adrenal insufficiency should be made only with corticotropin stimulation testing to assess adrenal reserve capacity.
The corticotropin stimulation test involves I.M. or I.V. administration of cosyntropin with samples obtained 60 minutes later. Cortisol levels should be greater than 18 µg/dl. If the result is abnormal, primary and secondary adrenal insufficiency can be distinguished by measuring aldosterone levels from the same blood sample. With secondary adrenal insufficiency, the aldosterone level is normal (greater than or equal to 5 ng/dl). Baseline plasma cortisol levels may also be obtained. With Addison’s disease, plasma and urine cortisol levels fail to rise normally in response to corticotropin; with secondary hypofunction, repeated doses of corticotropin over successive days produce a gradual increase in cortisol levels until normal values are reached.
Treatment
For all patients with primary or secondary adrenal hypofunction, lifelong corticosteroid replacement, usually with cortisone or hydrocortisone (both of which also have a mineralocorticoid effect) is the primary treatment.
For patients with Addison’s disease, treatment with oral fludrocortisone, a synthetic mineralocorticoid, is necessary to prevent dangerous dehydration, hypotension, and electrolyte disturbances with hyponatremia and hyperkalemia. (See Avoiding adrenal crisis.)
For those with adrenal crisis, prompt I.V. bolus administration of 100 mg of hydrocortisone is key. Later, 50- to 100-mg doses are given I.M. or are diluted with dextrose in saline solution and given I.V. until the patient’s condition stabilizes; up to 300 mg/day of hydrocortisone and 3 to 5 L of I.V. saline solution are required during the acute stage of adrenal crisis.
With proper treatment, adrenal crisis usually subsides quickly; the patient’s blood pressure stabilizes, and water and sodium levels return to normal. After the crisis, maintenance doses of hydrocortisone preserve physiologic stability.
Special considerations
If the patient is experiencing 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 the blood glucose level periodically because steroid replacement may necessitate adjustment of the insulin dosage.
Because the patient may have volume depletion, you’ll want to carefully record weight and intake and output. While waiting for the mineralocorticoid to take effect, make sure the patient gets plenty of fluids to compensate for excessive fluid loss, and make sure his sodium intake is increased.
CLINICAL TIP: If the patient also has an acute medical illness or is undergoing a surgical procedure, he’ll require additional steroids to cover these stressful periods.
To manage a patient receiving maintenance therapy:
Advise the patient to watch for symptoms of adrenal crisis, and tell the patient how to provide the necessary self-care upon discharge from the facility.
Arrange for a diet that maintains a balance of sodium and potassium.
If the patient is receiving a steroid, monitor him for cushingoid signs, such as fluid retention around the eyes and face. Watch for fluid and electrolyte imbalance, especially if the patient is receiving a mineralocorticoid. Monitor his weight and blood pressure to assess body fluid status. Be aware that steroid administration in the late afternoon or evening may stimulate the central nervous system and cause insomnia in some patients.
If the patient receives only a glucocorticoid, observe him for orthostatic hypotension or electrolyte abnormalities, which may indicate a need for mineralocorticoid therapy.
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Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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