Cushing's disease

Cushing's disease
Classification and external resources
ICD-10	E24.0

Cushing's disease is a cause of Cushing's Syndrome characterised by increased secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary. This is most often as a result of a pituitary adenoma. Pituitary adenomas are responsible for 70% of endogenous Cushing's syndrome,^[1] that is, when excluding Cushing's syndrome from exogenously administered corticosteroids, which is the major cause of Cushing's syndrome.

Signs and Symptoms

The condition is characterised by mainly the same features as Cushing's Syndrome with the added condition that ACTH levels are also elevated, despite the elevated levels of glucocorticoids such as cortisol.

History

The Soviet neurologist Nikolai Mikhailovich Itsenko in 1924 reported two patients.^{[citation needed]} The American surgeon Harvey Cushing in 1932 described the clinical syndromes.^{[citation needed]}

Diagnosis

Diagnosis is made first by diagnosis of Cushing's Syndrome which involves the 1 mg dexamethasone suppression test. If the patient has Cushing's Syndrome, the 8 mg dexamethasone suppression test is carried out which will confirm the aetiology of the disease.

Following the 8 mg dexamethasone suppression test plasma cortisol should be low; while plasma ACTH should be at the higher end of normal or should exceed the reference range. This will distinguish whether the cause is an ectopic ACTH secreting tumour, an adrenal carcinoma or an adrenal adenoma - ranges differ between different labs.

A CT or MRI of the pituitary may also show the ACTH secreting tumour if present.

Administration of corticotropin releasing hormone (CRH) can differentiate this condition from ectopic ACTH secretion. If ectopic, the plasma ACTH and cortisol levels should remain unchanged; if this is pituitary related, levels of both would rise.

Treatment

Treatment of a pituitary adenoma would probably involve surgery (transphenoidal hypophysectomy).

See also

• Cushing's syndrome
• Hyperpituitarism

References

1. ^ Cushing’s Syndrome at The National Endocrine and Metabolic Diseases Information Service. July 2008. In turn citing: Nieman LK, Ilias I. Evaluation and treatment of Cushing’s syndrome. The Journal of American Medicine. 2005;118(12):1340–1346.