Causes of Cushing's Syndrome

Causes of Cushing's Syndrome are as follows:

Looking at causes of Cushing Syndrome on basis of plasma ACTH levels, later helps in understanding the approach to investigations performed in diagnosis of Cushing's disease.

First use of exogenous steroids should be ruled out. Iatrogenic use of steroids is common cause of Cushing's Syndrome. Exogenous steroids cause feedback inhibition of ACTH secretion.

If plasma ACTH level is undetectable and there is no exogenous use of steroids then the source of increased cortisol level is likely an adrenal adenoma/ cancer / hyperplasia. The feedback inhibition due to increased cortisol levels make ACTH levels undetectable.

If ACTH levels are increased then it means the cause of high cortisol levels is high ACTH levels. This increased ACTH is due to either pituitary cause or ectopic ACTH secretion.

What are causes of ectopic ACTH secretion?

Ectopic ACTH secretion is most likely caused by small cell cancer of lung, or by carcinoid tumor.

What is the difference between Cushing's Syndrome and Cushing's Disease?

Cushing's disease is one of the causes of Cushing's Syndrome.

Cushing's Syndrome is a clinical state caused by increase in cortisol levels irrespective of the cause. If this increase in cortisol is caused by increase in ACTH secretion by a pituitary adenoma then it is known as Cushing's disease.

Cushing disease is most common endogenous cause of Cushing's syndrome.

Rare causes: Some of other causes of Cushing's syndrome with decreased ACTH levels are Carney complex, McCune Albright Syndrome. Rarely ectopic CRF production by rare thyroid and prostate cancer causes increased ACTH and increased cortisol production.

How to make a diagnosis of Cushing's Disease?

Tags: endocrinology, adrenal glands, Cushing, Pathology review notes, Medical school notes free, free pathology.

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