Cushing's syndrome Flashcards
What are three ectopic tumors that can produce ACTH and can give a patient Cushing’s syndrome?
Small cell lung cancer
Pancreatic islet cells
Thymomas
What is Cushing’s disease caused by?
- Pituitary adenoma causing ACTH overproduction
- Adrenal adenoma
- ectopic ACTH production (small cell lung cancer)
Why does Cushing’s syndrome cause HYPOkalemia?
In Cushing’s, there is high levels of cortisol.
At high levels, cortisol can act as a mineralcorticoid (aldosterone) stimulating the absorption of sodium and excretion of potassium.
Why does Cushing’s present with increased BP?
Excess cortisol causes cortisol to act like a mineralcorticoid (aldosterone), which leads to the absorption of sodium and an increased BP
Will a patient with Cushing’s present with bone pain?
Excess cortisol leads to severe muscle, bone and skin breakdown
Does Cushing’s result in elevated blood glucose levels?
Yes, which leads to high insulin levels, resulting in central obesity.
How does cortisol affect the immune system?
Excess cortisol also dampens the inflammatory and immune response, making individuals more susceptible to infections
How can small cell lung cancer and carcinoid tumors produce Cushing syndrome?
Small cell lung cancer and carcinoid tumors may produce Cushing syndrome due to paraneoplastic adrenocorticotropic hormone (ACTH) secretion
What are side effects of Cushing syndrome?
Fat redistribution (buffalo hump, moon facies), pigmented striae, obesity, skin atrophy, weight gain, easy bruising, elevated glucose, infections, cataracts, and hirsutism
What are two tests used to rule out Cushing’s syndrome?
- 24-hour free cortisol urine test (GOLD STANDARD)
- Dexamethasone suppression test
What is the GOLD STANDARD test in order to diagnose Cushing syndrome?
Twenty-four-hour urine test → Gold standard test
A test in which urine is collected for 24 hours to measure the amounts of cortisol. A higher than normal amount in the urine may be a sign of disease in the adrenal cortex
Low- dose dexamethasone suppression test:
A test in which one or more small doses of dexamethasone are given. The level of cortisol is checked from a sample of blood or from urine that is collected over three days. This test is done to check if the adrenal gland is making too much cortisol.
In general, a clear failure to suppress cortisol levels in response to low-dose dexamethasone establishes the diagnosis.
How does the dexamethasone suppresion test help in the diagnosis of Cushing syndrome?
Dexamethasone is an exogenous steroid that suppresses ACTH production.
How is Cushings and Addison’s disease similar?
Cushing’s → Twenty-four-hour urine test, but can give low dose dexamethasone suppression test.
(Serum levels will remain unchanged in Cushing’s)
ACTH-124 (Cosyntropin) with exogenous ACTH to distinguish between primary and secondary/tertiary adrenal insufficiency. The normal response is a rise in blood and urine cortisol levels after ACTH is given. A poor response suggests adrenal insufficiency.
Poor response in both
If a patient with Cushing’s syndrome has a positive low-dose suppresion test, what do you do next?
High-dose dexamethasone suppression test?
ACTH levels: Decreased ACTH = adrenal tumor, normal or increased ACTH means ectopic ACTH-producing tumor
