Cushing's Syndrome Flashcards
Cushing’s syndrome refers to feature of prolonged high levels of..
glucocorticoids
What are the 2 groups of corticosteroids?
Glucocorticoids and mineralocorticoids
Give an example of a glucocorticoid
cortisol
Give an example of a mineralcorticoid
aldosterone
Cortisol is the primary natural glucocorticoid hormone and is produced by the…
adrenal glands
Cushing’s disease refer to a ______ _______ secreting excessive ____
pituitary adenoma, ACTH
How does the increased ACTH in Cushing’s affect the adrenal glands?
Causes excessive cortisol to be released
What is the other cause (not Cushing’s disease ie pituitary adenoma) that can cause Cushing’s syndrome?
prolonged use of exogenous corticosteroids like prednisolone or dexamethasone.
What are features of Cushing’s syndrome?
Round face (“moon face”)
Central obesity
Proximal limb muscle wasting
Abdominal striae
Enlarged fat pad on upper back (“buffalo hump”)
Male pattern facial hair in women
Easy bruising
Poor skin healing
Hyperpigmentation of skin
What are metabolic effects of Cushing’s syndrome?
Hypertension (high levels of cortisol)
Cardiac hypertrophy
T2 DM (cortisol promotes insulin resistance)
Dyslipidaemia
Osteoporosis (cortisol inhibits osteoblasts)
What are the causes of Cushing’s Syndrome?
Think CAPE
Cushing’s disease (pituitary adenoma releasing excessive ACTH)
Adrenal adenoma (adrenal tumour secreting excess cortisol)
Paraneoplastic syndrome (a tumour secretes ACTH)
Exogenous steroids (long-term corticosteroids)
What does ectopic mean?
In an abnormal place or position
What is the ACTH from a tumour other than the pituitary gland (paraneoplastic syndrome) called?
Ectopic ACTH
How can hyperpigmentation help you diagnose?
Causes involving excess ATCH will show hyperpigmentation.
Therefore, Cushing’s disease (pituitary adenoma), paraneoplastic syndrome (ectopic ACTH) or Addison’s disease (lots of ACTH) will show hyperpigmentation.
However, there is not excess ACTH in an adrenal adenoma or exogenous steroids so no hyperpigmentation.
What test is used to diagnose Cushing’s syndrome caused by a problem in the body (ie not exogenous steroid use)
Dexamethasone suppression test
What is the normal response to dexamethasone?
Suppressed cortisol. due to negative feedback.
Dexamethasone suppresses both the CRH released by hypothalamus and the ACTH made by the pituitary gland. Therefore low cortisol level.
A lack of _____ suppression in response to dexamethasone suggests Cushing’s syndrome
cortisol
What is the low-dose overnight dexamethasone test?
1mg dexamethasone given at night and cortisol checked 9am.
Normal result = suppressed cortisol
Screening test
What is the low-dose 48 hour dexamethasone test?
0.5mg dexamethasone given every 6 hours for 8 doses starting 9am.
Cortisol checked before 1st dose at 9am and 9am after last dose.
Normal result = suppressed cortisol
What is high-dose 48 hour dexamethasone test?
2mg dexamethasone given every 6 hours for 8 doses.
This higher dose is enough to suppress cortisol in pituitary adenoma (Cushing’s disease) but not from adrenal adenoma or ectopic ACTH.
What happens to the level of ACTH when there is excess cortisol from an adrenal tumour or exogenous steroids?
It is suppressed
What happens to the level of ACTH when there is a pituitary tumour or ectopic ACTH?
It increases
What are other investigations for suspected Cushing’s disease?
Full blood count (may show high WBCs)
U&Es (may show low potassium if adrenal adenoma also secreting aldosterone)
MRI for pituitary adenoma
CT chest for small cell lung cancer (paraneoplastic syndrome)
CT abdomen for adrenal tumours
How do treat Cushing’s syndrome?
Surgery: remove adrenal tumour or ectopic ACTH. Trans-sphenoidal surgery for pituitary adenoma.
If surgical removal not possible then could remove both adrenal glands and give life-long steroid replacement therapy.
