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Addison's disease

primary adrenocortical deficiency

Addison's disease occurs when the adrenal glands, seated above the kidneys, fail to produce enough of the hormone cortisol and, sometimes, the hormone aldosterone.

Overview

There are two forms of Addison's disease, based on the reason for the disorder. Primary adrenal insufficiency occurs when the adrenal glands themselves are not working properly; secondary adrenal insufficiency occurs when the pituitary gland does not produce enough adrenocorticotropic hormone (ACTH) to adequately stimulate the adrenal glands.

Clinical suspicion

Suspect when fatigue, light headedness is accompanied by weight loss (weight gain excludes the diagnosis). This suspicion is strengthened when accompanied by postural hypotension, hyperpigmentation, hyperkalemia, hyponatremia and hypoglycemia. Some patients may present with esinophilia. Other symptoms include vomiting and abdominal pain.

Symptoms and signs

Addison's disease (also known as chronic adrenal insufficiency, or hypocortisolism) is a rare endocrine disorder. It is estimated that it affects about 1 to 5 in 100,000 people.

Addison's disease progresses slowly, and symptoms may not present or be noticed until some stressful illness or situation occurs. Common symptoms are:

  • chronic fatigue that gradually worsens
  • muscle weakness
  • loss of appetite
  • weight loss
  • nausea/vomiting
  • diarrhea
  • low blood pressure that falls further when standing (orthostatic hypotension)
  • areas of hyperpigmentation (darkened skin)
  • irritability
  • depression
  • craving for salt and salty foods
  • hypoglycaemia (worse in children)
  • for women, menstrual periods that become irregular or that stop

Diagnosis

Once suspected investigations should be urgent, a blood sample is taken for measurement of plasma cortisol and serum electrolytes. Hydrocortisone should be given IM.

Serum cortisol taken at 8:00am < 5ug/dL [SI:140nmol/L] (some authorities say < 3ug/dL [SI: 86nmol/L]) confirms the diagnosis. A result of > 20ug/dL [SI: 550nmol/L] excludes the diagnosis in an unstressed individual.

Between these values if the condition is still suspected a rapid ACTH stimulation test should be performed. When impaired a long ACTH stimulation test should be performed to differentiate primary from secondary insufficiency.

A high plasma ACTH level with a low or normal cortisol level confirms primary adrenocortical insufficiency.

Treatment

Treatment for Addison's disease basically involves replacing the missing cortisol and, if necessary, providing replacement therapy for the missing aldosterone. Caution must be exercised when the person with Addison's disease has surgery or becomes pregnant.

Addisonian crisis

An illness or accident can aggravate the adrenal problems and cause an Addisonian crisis in which the symptoms include:

  • sudden penetrating pain in the legs, lower back or abdomen
  • severe vomiting and diarrhea, resulting in dehydration
  • low blood pressure
  • loss of consciousness

Untreated, an Addisonian crisis can be fatal.

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