Cushing's disease
Encyclopedia
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, that is, when excluding Cushing's syndrome from exogenously administered corticosteroids, which is the major cause of Cushing's syndrome.
.
in 1932 described the clinical syndromes.
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.
).
Cushing's syndrome
Cushing's syndrome is a hormone disorder caused by high levels of cortisol in the blood. This can be caused by taking glucocorticoid drugs, or by tumors that produce cortisol or adrenocorticotropic hormone or CRH...
characterised by increased secretion of adrenocorticotropic hormone
Adrenocorticotropic hormone
Adrenocorticotropic hormone , also known as 'corticotropin', 'Adrenocorticotrophic hormone', is a polypeptide tropic hormone produced and secreted by the anterior pituitary gland. It is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological...
(ACTH) from the anterior pituitary
Anterior pituitary
A major organ of the endocrine system, the anterior pituitary, also called the adenohypophysis, is the glandular, anterior lobe of the pituitary gland...
. This is most often as a result of a pituitary adenoma
Adenoma
An adenoma is a benign tumor of glandular origin. Adenomas can grow from many organs including the colon, adrenal glands, pituitary gland, thyroid, prostate, etc. Although these growths are benign, over time they may progress to become malignant, at which point they are called adenocarcinomas...
. Pituitary adenomas are responsible for 70% of endogenous Cushing's syndrome, 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 cortisolCortisol
Cortisol is a steroid hormone, more specifically a glucocorticoid, produced by the adrenal gland. It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat,...
.
History
The Soviet neurologist Nikolai Mikhailovich Itsenko in 1924 reported two patients. The American surgeon Harvey CushingHarvey Cushing
Harvey Williams Cushing, M.D. , was an American neurosurgeon and a pioneer of brain surgery, and the first to describe Cushing's syndrome...
in 1932 described the clinical syndromes.
Diagnosis
Diagnosis is made first by diagnosis of Cushing's Syndrome which involves the 1 mg dexamethasoneDexamethasone
Dexamethasone is a potent synthetic member of the glucocorticoid class of steroid drugs. It acts as an anti-inflammatory and immunosuppressant...
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
Cortisol
Cortisol is a steroid hormone, more specifically a glucocorticoid, produced by the adrenal gland. It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat,...
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 hypophysectomyHypophysectomy
Hypophysectomy is the surgical removal of the hypophysis . It is most commonly performed to treat tumors, especially craniopharyngioma tumors. Sometimes it is used to treat Cushing's syndrome due to pituitary adenoma...
).