Wednesday, May 3, 2017

Adrenal Hypofunction

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.
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.
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.
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.
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.
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.

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