Adrenal insufficiency Flashcards
what does CRH stand for?
corticotropin-releasing hormone
what does ACTH stand for?
adrenocorticotropic hormone
what is CRH, and hence cortisol release in response to?
circadian rhythm (light-dark), stress + other factors
where does the eye convey info to (circadian rhythm) and what are glucocorticoid’s role?
eye –> SCN (suprachiasmatic nuclei)
glucocorticoids are the secondary messenger from central –> peripheral clock
cortisol effects
Increase blood sugar through gluconeogenesis
Suppress the immune system
Aids in the metabolism of fat, protein, and carbohydrates
Decreases bone formation.
Na retention, increased renal K loss
Help body respond to stress
what are synthetic steroids used in?
many inflammatory disorders and replacement therapy in adrenal insufficiency
e.g. cortisol, prednisolone, methylprednisolone + dexamethasone
what is addison’s disease?
EMERGENCY
primary hypoadrenalism
rare
destruction of the entire adrenal cortex
cause of addison’s disease
90% - destruction by organ-specific autoantibodies
rarer: adrenal gland TB, surgical removal, haemorrhage, malignant infiltration
clinical presentation addison’s disease
postural hypotension (head rush)
hyper pigmentation
vitiligo + loss of body hair in women
what is an addisonian crisis?
vomiting, abd pain, profound weakness, hypoglycaemia
what causes postural hypotension?
salt + water loss
what causes hyper pigmentation?
stimulation of melanocytes by excess ACTH in primary hypoadrenalism
what causes vitiligo + loss of body hair in women
dependence on adrenal androgens
3 principles of investigating/diagnosing hypoadrenalism
- demonstrate low cortisol secretion
- find out if its dependent/independent on ACTH secretion
- specific cause of adrenal failure
Investigations for diagnosis of addison’s disease
single cortisol measurements (not that useful)
***short ACTH (tetracosactide) stimulation test is KEY
plasma ACTH level
adrenal antibodies
hyponatraemia, hyperkalaemia
results of plasma ACTH level and what they mean
if high with low/low-normal cortisol - confirms primary hypoadrenalism
what may a CXR + AXR show for Addison’s disease
TB
calcified adrenals
Mx Addison’s disease
lifelong steroid replacement (tablets)
- hydrocortisone: morning + eve –> mimics normal diurnal rhythm
- fludrocortisone: synthetic mineralocorticoid
Additional Mx Addison’s disease
Medic Alert bracelet/necklace
Increase steroid dose in stress: trauma, surgery, infection
(as in a normal person, ACTH would be up-regulated in these situations)
Causes of secondary adrenal insufficiency
- hypothalamic-pituitary disease
2. long-term steroid therapy leading to hypothalamic-pituitary-adrenal suppression
Clinical features secondary adrenal insufficiency
Same as Addisons
BUT no pigmentation because ACTH levels are low
How does the long ACTH test help in the diagnosis of secondary adrenal insufficiency
differentiates between primary and secondary adrenal failure
- normal adrenal glands –> reach certain levels of plasma cortisol conc by 4hrs
- primary: cortisol response is impaired throughout
- secondary: delayed but normal response is seen
Tx secondary adrenal insufficiency
hydrocortisone (?can be IV or s/c)
fludrocortisone is unneccssary
what happens if adrenal failure is secondary to long-term steroid therapy?
they will recover if steroids are withdrawn very slowly
