Cushing's syndrome
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Cushing's syndrome or hypercortisolism is an endocrine disorder caused by excessive levels of the endogenous corticosteroid hormone cortisol. It may also be induced iatrogenically by treatment with exogenous corticosteroids for other medical conditions.
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Signs and symptoms
Symptoms include weight gain, particularly of the trunk and face with sparing of the limbs (central obesity), "moon face", excess sweating, telangiectasia (dilation of capillaries), atrophy of the skin (which gets thin and bruises easily) and other mucous membranes, purple striae on the trunk and bottocks, proximal muscle weakness (hips, shoulders), and hirsutism (male-pattern hair growth). The excess cortisol may also affect other endocrine systems and cause, for example, reduced libido, impotence, amenorrhoea, infertility and insulin resistence, which is believed to be a diabetogenic effect. Patients frequently suffer various psychological disturbances, ranging from euphoria to frank psychosis.
Signs include persistent hypertension (due to the aldosterone-like effects) and insulin resistance, leading to hyperglycemia (high blood sugars); many develop frank diabetes).
Diagnosis
When Cushing's is suspected, both a dexamethasone suppression test (administration of dexamethasone and frequent determination of cortisol and ACTH levels) and 24-hour urinary measurement for cortisol have equal detection rates. A novel approach is sampling cortisol in saliva over 24 hours, which may be equally sensitive. Other pituitary hormones may need to be determined, and performing physical examination directed for any visual field defect may be necessary if a pituitary lesion is suspected (which may compress the optic chiasm causing typical bitemporal hemianopia). But, we must keep in mind that marcoadenomas (lesions larger than 1cm) are mostly no-functioning tumor.
When these tests are positive, CT scanning of the adrenal gland and MRI of the pituitary gland are performed. These should be performed when other tests are positive, to decrease likelihood of incidentalomas (incidental discovery of harmless lesions in both organs). Scintigraphy of the adrenal gland with iodocholesterol scan is occasionally necessary. Very rarely, determining the cortisol levels in various veins in the body (employing catheterisation) is necessary.
Pathophysiology
Cortisol is secreted by the adrenal glands under regulation by the pituitary gland and hypothalamus. Strictly, Cushing's syndrome refers to excess cortisol of any etiology. Cushing's disease refers only to hypercortisolism secondary to excess production of adrenocorticotropin (ACTH) from a pituitary gland adenoma.
Therapy
If an adrenal adenoma is identified it may be removed by surgery. Post-operatively most patients will require steroid replacement at least in the interim as long-term suppression of pituitary ACTH and normal adrenal tissue does not recover immediately. Clearly, if both adrenals are removed replacement with hydrocortisone or prednisolone is imperative.
In those patients not suitable for or unwilling to undergo surgery, several drugs have been found to inhibit cortisol sythesis (e.g. ketoconazole, metyrapone) but they are of limited efficacy.
In iatrogenic Cushing's, dose adjustment may be sufficient or it may be necessary to change to another type of immunosuppresive medication.
Epidemiology
Iatrogenic Cushing's syndrome (caused by treatment with corticosteroids) is the most common form of Cushing's syndrome. Endogenous (i.e. non-iatrogenic) Cushing's syndrome is relatively rare.
Incidence of causes of Cushing's syndrome per million person-years: -
- Cushing's disease: 10
- Primary adrenal: 3
- Ectopic ACTH: 1.4
See also
The converse situation of primary adrenal insufficiency is known as Addison's Disease--which afflicted John F. Kennedy.
External links
- Cushing's Syndrome (http://www.niddk.nih.gov/health/endo/pubs/cushings/cushings.htm)
- Cushing's syndrome (http://www.surgical-tutor.org.uk/default-home.htm?system/hnep/cushings.htm~right)
- Cushing's Syndrome/Disease in dogs (http://www.io.com/~lolawson/cushings/)
- Cushing's Syndrome and Cushing's Disease (http://cushings.homestead.com/)de:Cushing-Syndrom
id:Sindrom Cushing ms:Sindrom Cushing nl:Syndroom van Cushing pt:Síndrome de Cushing