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Flashcards in 21. Cushing syndrome Deck (36)

Cushing syndrome

increased cortisol due to a variety of causes


causes of increased cortisol

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


MC cause of increased cortisol ( Cushing syndromeO

exogenous cortisol


exogenous cortisol results in

1. decreased ACTH
2. bilateral adrenal atrophy


Primary adrenal adenoma / hyperplasia / carcinoma results in

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


pseudohyperaldosteronism is characterized by

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


Paraneoplastic ACTH secretion - examples

1. small cell lung cancer
2. bronchial carcinoids


Paraneoplastic ACTH secretion results in

1. increased ACTH
2. bilateral adrenal hyperplasia


ACTH- secreting pituitary adenoma may results in

1. increased ACTH
2. bilateral adrenal hyperplasia


Cushing disease

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


MCC of endogenous cases of Cushing syndrome

Cushing disease ( ACTH - secreting pituitary adenoma)


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


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


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

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


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

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


Cushing disease ectopic ACTH : how to differentiate

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


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

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


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

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


High dose dexamrhason suppression test - dose ?

8 mg


ectopic ACTH secretion will not decrease with dexamethasone because

the source is resistant to negative feedback


ectopic ACTH secretion will not increase with CRH because

pituitary ACTH is suppressed


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


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)


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)


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


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)


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)


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


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)


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


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)


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


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


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


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


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.