16. Cushing syndrome Flashcards
what is the definition of cushing syndrome ?
chronic exposure to excessive glucocorticoids - cortisol = hyprcortisolism
it is the loss circadian rhythm and loss of normal negative feedback in the hypothalamic pitutory adrenal axis
what i the normal physiology of cortisol release ?
cortisol is released in CRICARDIAN RHYTHMS = PEAK AT 7-8AM
and then fall reaching its lowest and midnight
and begin to rise again at 2 am
what is the etiology of cushing syndrome ?
Primary hypercortisolism - ACTH INDEPENDANT
LEAST COMMON
= adrenal adenoma = macrronodular adrenal hyperplasia =primary pigment nodular adrenal disease = associated with McCuney albright syndrome = develops only in infancy ============== secondary hypercortisolsim ACTH DEPENDANT
1) PITUATRY acth production
MOST COMMON
pituitary adenomas
2) ECTOPIC ACTH
second most common
small cell lung carcinoma
renal cell carcinoma
exogenous ACTH administration
exogenous glucocorticoid administration
what is the clinical manifestation of cushing syndrome ?
proximal muscle weakness red cheeks and moon face buffalo hump spontaneous eechymosis purple striae poor wound healing thin arms and legs with central obesity high blood pressure
delayed puberty and growth retardation
what are the complications of cushing syndrome
cardiovascular diseases = hypertension , artherosclerosisi cardiomyopathy
dyslipidemia
insulin resistenacy -diabetes
cataract , glaucoma
nephrolithiasis
how can we diagnose cushing syndrome ?
to get these results
1mg of midnight dexamethasone suppression test = exogenous administration of glucocorticoid leads to suppression of the HPA axis
measured at 9 o clock
serum cortisol less than 1.8mg/dl = normal
midnight salivary cortisol test
24hr urinary free cortisol = atleast 2
9 o clock ACTH measurements
normal or high ACTH = MRI SCAN OF PITUTORY
if low acth = imaging of adrenals
inferior petrosal sinus sampling (IPSS) is an invasive procedure in which adrenocorticotropic hormone (ACTH) levels are sampled from the veins that drain the pituitary gland; these levels are then compared with the ACTH levels in the peripheral blood to determine whether a pituitary tumor or ectopic ACTH
what are pseudo cushing syndrome ?
patient presents with clinical features suggestive of true Cushing’s syndrome and with some biochemical evidence of hypercortisolaemia without the condition
PHYSIOLOGICAL HYPERCOTISOLISM
what causes pseudo cushing syndrome ?
it is not caused by a problem in the HPA AXIS
uncontrolled diabetes
alcoholism esp withdrawal
psychiatric disorders
what is the treatment of cushing syndrome ?
surgery of pituitary adenoma and adrenal adenoma
inoperable condition
adrenal enzyme inhibitors = ketoconazole
Etomidate
Mitotane
Glucocorticoid receptor antagonist: mifepristone
why does cortisol levels rise at night ?
cortisol is the hormone that helps you to keep your glucose levels high enough during your sleep
