Cushing Adenoma

Cushing s Disease) ACTH Syndrome Administration Adenoma Carcinoma... 

ACTH-dependent Cushing s syndrome is usually caused by overproduction of ACTH by the pituitary gland, causing adrenal hyperplasia (Cushing s disease). Pituitary adenomas account for about 80% of these cases. Ectopic ACTH-secreting tumors and nonneoplastic corticotropin hypersecretion are responsible for the remaining 20% of cases. 

ACTH-independent Cushing s syndrome is usually caused by adrenal adenomas and carcinomas. 

Cushing s disease (caused by a pituitary ACTH-secreting adenoma) or Cushing s syndrome from an adrenal tumour is normally treated by surgical removal of the primary lesion where possible. Cases of ectopic ACTH syndrome associated with carcinoma of the bronchus cannot be treated surgically, and often benefit from medical therapy to control adrenal steroid excess. 

Metyrapone is commonly used in tests of adrenal function. The blood levels of 11-deoxycortisol and the urinary excretion of 17-hydroxycorticoids are measured before and after administration of the compound. Normally, there is a twofold or greater increase in the urinary 17-hydroxycorticoid excretion. A dose of 300-500 mg every 4 hours for six doses is often used, and urine collections are made on the day before and the day after treatment. In patients with Cushing s syndrome, a normal response to metyrapone indicates that the cortisol excess is not the result of a cortisol-secreting adrenal carcinoma or adenoma, since secretion by such tumors produces suppression of ACTH and atrophy of normal adrenal cortex. 

Because of its effects on the pituitary/adrenal system, ketoconazole has been used in the long-term control of hypercortisolism of either pituitary or adrenal origin (SED-12, 677). In seven patients with Cushing s disease and one with an adrenal adenoma, ketoconazole 600-800 mg/day for 3-13 months produced rapid persistent clinical improvement (585). Plasma dehydroepiandrosterone sulfate concentrations and urinary 17-ketosteroid and cortisol excretion fell soon after the start of treatment, and remained normal or nearly so throughout treatment. Urinary tetrahydro-ll-deoxycortisol excretion rose... 

Cushing s syndrome (hypercorticism) is an endocrine hormone disorder caused by high levels of cortisol in the blood. Cushing s disease refers to one specific cause, a non-cancerous tumour (adenoma) in the pituitary gland that produces a large amount of ACTH, which in turn elevates cortisol. It can usually be cured by surgery. 

ACTH-independent Cushing s syndrome shows increased cortisol, but the ACTH is not elevated but rather decreased due to negative feedback. It can be caused by exogenous administration of glucocorticoids or by adrenal adenoma, carcinoma or nodular hyperplasia. 

Features include muscle weakness and cramps, paraesthesia, nausea, vomiting, constipation, abdominal pain, polyuria, polydipsia, depression, confusion and psychosis. Hypokalaemia may cause brady/tachyarrhythmias, hypotension, respiratory failure, ileus and altered mental state. It also increases the toxicity of cardiac glycosides. There are several associated disease states (e.g. diarrhoea, vomiting, renal tubular acidosis types I and II, hypomagnesaemia, Conn s syndrome, Cushing s disease, Gitelman s syndrome, villous adenoma, pyloric stenosis, intestinal fistulae). 

These agents have use in diagnosis of adrenal disease and in controlling excessive production of corticosteroids, e.g. by corticotropin producing tumours of the pituitary (Cushing s syndrome) or by adrenocortical adenoma or carcinoma where the cause cannot be removed. They must be used with special care since they can precipitate acute adrenal insufficiency. Some members inhibit other steroid synthesis. 

Corticotrophin releasing hormone (CRH), corti-coliberin, is a hypothalamic polypeptide that has diagnostic use. It increases ACTH secretion in Cushing s disease secondary to pituitary ACTH-secreting adenoma. It has no therapeutic use. 

Reed S M 1998 Pituitary adenomas equine Cushing s disease. In Reed S M, Bayly W M (eds) Equine internal medicine. Saunders, Philadelphia, PA, pp. 912-916... 

Primary adrenal adenoma (Cushing s syndrome) Pituitary adenoma secreting ACTH (Cushing s disease) Exogenous cortisol therapy Excessive licorice ingestion Bartter s syndrome (defective renal CL reabsorption)... 

Rationale Patients with Cushing s syndrome caused by an ACTH-producing pituitary adenoma usually show suppression of cortisol with high-dose dexamethasone. Patients with Cushing s syndrome from other causes (adrenocortical adenoma, adrenocortical carcinoma, or ectopic production of ACTH) usually do not demonstrate any change in cortisol concentration. 

The remaining 18% of Cushing s syndrome cases are ACTH-independent and are almost equally divided between adrenal adenomas and adrenal carcinomas, with rare cases caused by micronodular or macronodular hyperplasia." The majority of adrenal cortex tumors are benign adenomas. Adrenal carcinoma is found more often in children than in adults with Cushing s syndrome. 

During the last decade, the treatment of choice for Cushing s disease has been transsphenoidal resection of the pituitary micro-adenoma." The advantages to this procedure include preservation of pituitary function, low complication rate, and high clinical improvement rate. The overall cure rate of histologically proven tumors approaches 90%. 

This patient presents with many of the classic findings of Cushing syndrome. Adrenal hyperplasia can be caused by excessive stimulation from ACTH (pituitary or ectopic production) or from a primary adrenal problem such as adenomas/ carcinomas. In addition to above symptoms, patients with Cushing syndrome are also at risk for osteoporosis and diabetes mellitus (DM). The diagnosis is confirmed with elevated cortisol levels after a dexamethasone suppression test. Treatment depends on the underlying etiology and is often surgical. 

Cushing disease A specific form of Cushing syndrome, which is caused by an ACTH-secreting pituitary adenoma represents approximately 66 percent of all cases of Cushing syndrome. Because of structural similarities with melanocyte-stimulating hormone (MSH), excess ACTH from pituitary adenomas can induce dermal hyperpigmentation. 

Cushing syndrome is a rare condition in which elevated levels of cortisol are present in the patient for an extmded period of time (hypercortisolism). Typically, it affects those betweoi the ages of 20 and 50 years. On rare occasions, this disease may result from an inherited condition, which leads to growth of adenomas in endocrine glands, such as the adrenal, parathyroid, pancreas or pituitary glands. 

Cushing s disease where a pituitary adenoma secretes ACTH... 

Cushing s S)mdrome State of excess glucocorticoids caused by 1) overmedication with drugs listed above, 2) adrenal hypersecretion due to tumor, or 3) excessive ACTH release (pituitary adenoma or metastatic tumors). Results in osteoporosis, skin atrophy, abnormal fat distribution, abnormal glucose tolerance, behavioral abnormalities, euphoria. Diagnosed by dexamethasone suppression test (Table 10.6). 

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