21. Cushing syndrome Flashcards Preview

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Flashcards in 21. Cushing syndrome Deck (36):
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Cushing syndrome

increased cortisol due to a variety of causes

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causes of increased cortisol

1. exogenous corticosteroids
2. Primary adrenal adenoma/ hyperplasia/ carcinoma
3. ACTH- secreting pituitary adenoma ( Cushing disease)
4. Paraneoplastic ACTH secretion

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MC cause of increased cortisol ( Cushing syndromeO

exogenous cortisol

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exogenous cortisol results in

1. decreased ACTH
2. bilateral adrenal atrophy

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Primary adrenal adenoma / hyperplasia / carcinoma results in

1. decreased ACTH
2. atrophy of uninvolved adrenal
3. can present as pseudohyperaldosteronism

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pseudohyperaldosteronism is characterized by

by clinical picture of hyperaldosteronism with suppression of plasma renin activity and aldosterone

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Paraneoplastic ACTH secretion - examples

1. small cell lung cancer
2. bronchial carcinoids
3.ACTH

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Paraneoplastic ACTH secretion results in

1. increased ACTH
2. bilateral adrenal hyperplasia

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ACTH- secreting pituitary adenoma may results in

1. increased ACTH
2. bilateral adrenal hyperplasia

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Cushing disease

a specific type of Cushing 's syndrome caused by ACTH - secreting pituitary adenoma

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MCC of endogenous cases of Cushing syndrome

Cushing disease ( ACTH - secreting pituitary adenoma)

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Cushing syndrome - symptoms and findings (10)

1. hypertension
2. weight gain
3. moon facies
4. truncal obesity
5. buffalo hump
6. skin changes ( thinning, striae)
7. osteoporosis
8. hyperglycemia ( insulin resistance )
9. amenorrhoea
10. Immunosuppression

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Screening tests include for Cushing diagnosis

1. Increased free cortisol on 24h urinalysis
2. increased midnight salivary control
3. no suppression with overnight low-dose dexomethasone test

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diagnosis cause of Cushing - measure ACTH - suppressed --->

ACTH independent Cushing syndrome or exogenous ---> MRI to confirm adrenal tumor

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diagnosis of cause of endogenous tumor - measure ACTH - elevated --->

ACTH depended Cushing syndrome
Cushing disease or ectopic ACTH
High dose dexamethason suppresion test (8mg)
OR
CRH stimulation test

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Cushing disease ectopic ACTH : how to differentiate

High dose dexamethason suppression test ( 8mg)
OR CRH stimulation test

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Cushing disease ectopic ACTH ---> high dose dexamethason suppresion test --->

adequate suppresion ---> Cushing disease
No suppression --> ectopic ACTH

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Cushing disease ectopic ACTH --> CRH stimulation test --->

increased ACTH, cortisol --> Cushing disease NON increased on ACTH, cortisol ---> ectopic ACTH

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High dose dexamrhason suppression test - dose ?

8 mg

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ectopic ACTH secretion will not decrease with dexamethasone because

the source is resistant to negative feedback

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ectopic ACTH secretion will not increase with CRH because

pituitary ACTH is suppressed

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What is the difference between Cushing syndrome and Cushing disease?

Cushing syndrome: high cortisol level from any cause; Cushing disease: specific type caused by an ACTH-producing pituitary adenoma

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A man with Cushing syndrome has increased adrenocorticotropic hormone (ACTH). What are two possible mechanisms of his increased ACTH level?

ACTH-producing pituitary adenoma (Cushing disease), ectopic ACTH production (e.g., small cell lung cancer, bronchial carcinoid)

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A patient with Cushing syndrome has decreased ACTH. What are two mechanisms of increased cortisol production with a low ACTH level?

Exogenous steroids (primary cause) & adrenal overproduction of cortisol (e.g., adrenal adenoma, carcinoma, nodular adrenal hyperplasia)

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You administer a low dose of dexamethasone to a patient and his cortisol levels decrease. What do you expect to see after a high dose?

Cortisol suppression with high- and low-dose dexamethasone indicates normal cortisol function

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A patient's cortisol level remains high after a low dose of dexamethasone but is suppressed with a high dose. Diagnosis?

Adrenocorticotropic hormone–producing pituitary tumor (Cushing disease)

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What does dexamethasone testing before removal of a pituitary adenoma from a man with central obesity, abdominal striae, and diabetes show?

High cortisol with low dosing and reduced cortisol with high dosing, because this is a cortisol-producing pituitary tumor (Cushing disease)

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A man has Cushing syndrome. His cortisol increases after both low and high doses of dexamethasone. What are two possible diagnoses?

Cortisol-producing tumor or ectopic adrenocorticotropic hormone (ACTH)–producing tumor

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A CRH stimulation test is ordered for a patient with excess cortisol and elevated ACTH, and the ACTH level doesn't change. Why?

Because the patient has ectopic ACTH production (often seen in paraneoplastic syndromes)

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A man has a "buffalo hump" and elevated ACTH. You suspect Cushing disease. How does a high-dose dexamethasone suppression test support this?

Expected suppression of ACTH with high-dose dexamethasone suppression testing

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In a patient with moon facies and low ACTH, what diagnostic testing should you order next?

MRI to confirm presence of an adrenal tumor causing an ACTH-independent Cushing syndrome (ectopic cortisol production)

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Cushing syndrome develops in a patient with a remote history of an untreated adrenal gland tumor. What is the standard workup?

First. an ACTH check; if suppressed (<5 pg/mL), an MRI to confirm the presence of an adrenal tumor causing ACTH-independent Cushing syndrome

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A Cushing patient's ACTH level is <20 pg/mL. Brain MRI shows a pituitary mass. What will high-dose dexamethasone suppression test show?

If the mass is secreting ACTH (Cushing disease), there will be adequate suppression of ACTH release by dexamethasone

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A man has ACTH-dependent Cushing syndrome. Dexamethasone suppression testing does not suppress ACTH. What will a CRH stimulation test show?

The negative suppression result suggests ectopic ACTH release, so CRH stimulation will not increase ACTH

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A woman has ACTH-dependent Cushing syndrome. A CRH stimulation test promotes additional ACTH release. Do you perform a brain MRI?

Yes—a positive result on CRH stimulation testing suggests Cushing disease (ACTH-secreting pituitary tumor), so brain MRI is indicated

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Insulin resistance and truncal obesity develop in a patient on long-term anti-inflammatory meds. What will adrenal biopsy show?

Bilateral adrenal atrophy—this is Cushing syndrome due to long-term exogenous corticosteroid use.