Adrenal insufficiency

Adrenal insufficiency refers to inadequate secretion of corticosteroids (glucocorticoids and mineralocorticoids).

It may occur from partial or complete destruction of the adrenal cortex, in which case it is termed primary adrenal insufficiency (also known as Addison disease). Secondary adrenal insufficiency due to lack of stimulation of the gland is a more common aetiology overall.

Clinical presentation

Depends on the course of the disease:

• acute stage: the patient presents with fever, back pain, hypotension, weakness
• chronic stage: progressive lethargy, weakness, cutaneous pigmentation, weight loss

Laboratory data

• chemistry: hyponatremia, hyperkalemia, azotemia, hypercalcemia, hypoglycemia
• adrenocorticotrophic hormone (ACTH) stimulation test:
  • primary adrenal insufficiency
    • cortisol levels fail to rise after synthetic ACTH stimulation due to the destruction of the adrenal cortex
  • secondary adrenal insufficiency
    • cortisol levels rise after synthetic ACTH stimulation
    • this indicates decreased ACTH secretion due to pituitary dysfunction

Pathology

Primary

• idiopathic autoimmune disorders are the most common cause in developed countries (80% of cases) ¹
• granulomatous disease: tuberculosis (the most common infectious cause in developing countries) and sarcoidosis
• neoplasms: metastases (e.g. lung, ovary, kidney, melanoma), lymphoma, and leukaemia
• adrenal haemorrhage: shock, sepsis (Waterhouse-Friderichsen syndrome), coagulation disorders, antiphospholipid syndrome
• systemic fungal infection: histoplasmosis (most common in the southeastern and south-central United States ¹)
• adrenoleukodystrophy

Secondary

• suppression of the adrenal axis by endogenous or exogenous glucocorticoids
• hypothalamic or pituitary lesions

Time course

The disease course may be either acute, subacute, or chronic ²:

• acute: occurs within a few weeks to months and is caused by bilateral adrenal haemorrhage (adrenal apoplexy) or secondary to shock and sepsis or trauma (Addisonian crisis)
• subacute disease (adrenalitis): when the disease has been present for less than two years
• chronic: secondary to chronic autoimmune disorder or chronic granulomatous infection (tuberculosis)
  • the adrenal glands become atrophic and calcified

Radiographic features

Adrenal insufficiency is a bilateral process that cannot be diagnosed by imaging alone. CT would be the best imaging modality for adrenal assessment but is not necessary for diagnosis.

CT

Imaging features depend on the cause and the course of the disease either acute, subacute or chronic:

• acute: bilateral adrenal hematomas
• subacute (adrenalitis): enlargement of both adrenal glands, with necrotic centres and peripheral enhancing rims
• chronic: both adrenal glands appear small and atrophic, associated with calcifications (adrenal calcification) in granulomatous adrenalitis

Treatment and prognosis

• acute: glucocorticoid therapy, volume, and electrolyte replacement 
• chronic: glucocorticoid and mineralocorticoid replacement

Differential diagnosis

• adrenal metastasis and adrenal lymphoma
• adrenal hemorrhage
• adrenal adenoma