cushing syndrome Flashcards
what is cushing’s syndrome?
prolonged high levels of glucocorticoids in the body
what are the two groups of corticosteroid hormones?
- glucocorticoids eg cortisol
- mineralcorticoids eg aldosterone
how does a pituitary adenoma cause cushings syndrome?
- pituitary adenoma (tumour) secretes excessive ACTH
- this stimulates the cortisol release from the adrenal glands
what exogenous substance often causes cushings syndrome?
- prolongued use of exogeous corticosteroids
what features could be found upon inspection in someone with cushings syndrome?
- round face (moon face)
- central obesity
- abdominal strae (stretch marks)
- enlarged fat pad on the upper back (known as buffalo hump)
- proximal limb muscle wasting (difficulty standing from a sitting position without using their arms)
- male pattern facial hair in women (hirsutism)
- easy bruising and poor skin healing
- hyperpigmentation of the skin
what are some metabolic effects which cushing syndrome might cause in a patient?
- hypertension
- cardiac hypertrophhy
- type 2 diabetes
- dyslipideamia
- osteoporosis
what are some mental health effects which cushings syndrome might cause in a patient?
- anxiety
- depression
- insomnia
- rarely psychosis
what are the causes of Cushings syndrome and the nemonic?
CAPE
C - cushings disease - a pituitary adenoma (inc ACTH which in turn inc cortisol)
A - adrenal adenoma (inc cortisol)
P - paraneoplastic syndrome (ectopic ACTH - inc cortisol
E - exogenous steroids
paraneoplastic syndrome is a cause of Cushing’s syndrome, what is this?
- when ACTH is released from the tumour somewhere other than the pituitary gland
- this is called ectopic ACTH
- common in small lung cancer
- this stimulates excessive cortisol release from the adrenal glands
what is a dexamethasone suppression test?
- test to diagnose cushings syndrome
- not used for cushings syndrome caused by
how does a dexamethasone suppression test work?
- usually the hypothalamus releases CRH
- in turn stimulates the pituitary glands to secrete ACTH
- in turn stimulates the adrenal glands to secrete cortisol
- when dexamethasone is introduced, it has a negative feedback effect on CRH which should therefore reduce the ACTH and therefore lower the cortisol which is secreted
- in instances of cushings disease, cortisol levels wont drop
what are the 3 types of dexamethasone suppression tests and when are they used?
- low-dose overnight test (used as a screening to exclude cushings syndrome)
- low-dose 48-hour test (used in suspected cushings syndrome)
- high-dose 48-hour test (used to determine the cause in patients with confirmed cushings syndrome)
explain the procedure of the low-dose overnight test?
- 1mg of dexamethasone is given at night - usually 10/11pm
- cortisol levels will be assessed at 9am the following morning
- normal result is lowered cortisol levels
explain the procedure for the low-dose 48-hour test?
- 0.5mg of dexamethasone is taken every 6 hours for 8 doses
- starting at 9am
- cortisol is checked at 9am before first administration of the first day
- it is then checked at 9am on day 3
- a normal result is supressed cortisol, if its not, could be an indicator of cushings
explain the procedure for a high-dose 48-hour test?
- same as low-dose 48-hour test but using 2mg instead of 0.5mg of dexamethasone
- this higher dose is enough to supress the cortisol in cushings syndrome caused by cushing disease (pituitary adenoma) - but not when uts an adrenal adenoma or ectopic ACTH
