adrenal physiology Flashcards
causes of primary insufficiency
addison’s disease
congenital adrenal hyperplasia (CAH)
adrenal TB/malignancy
secondary (and tertiary) insufficiency
due to lack of ACTH stimulation
iatrogenic (excess exogenous steroid)
pituitary/hypothalamic disorders
clinical features of addison’s disease
anorexia, weight loss
fatigue/lethargy
dizziness and low BP
abdominal pain, vomiting, diarrhoea
skin pigmentation
commonest cause of PAI ?
addison’s
cause of addison’s
autoimmune destruction of adrenal cortex (90% destrtoyed before symptomatic, autoantibodies positive in 70%)
what other autoimmune diseases associated w/ addison’s ?
T1DM, autoimmune thyroid disease, pernicious anaemia
diagnosis of adrenal insufficiency
“suspicious biochemistry” (decrease Na, increase K) (hypoglycaemia)
“short synacthen test” (measueing plasma cortisol before and 30 mins after IV/IM ACTH injection)
what are ACTH levels in addison’s ?
should be high (causes skin pigmentation)
renin/ aldosterone levels in addisons ?
inc renin dec aldosterone
management of adrenal insufficiency
hydrocortisone as cortisol replacement
(iv first if unewell, usually 15-30mg daily in divided doses, try to mimic diurnal rhythm)
fludrocortisone as aldosterone replacement
(careful monitoring of BP and K)
adrenal crisis management
fluids - normal saline
100mg iv - steroids hydrocortisone 50mg IM every 6hrs or 24hr infusion
treat underlying cause
secondary adrenal insufficiency (lack or CRH/ACTH) causes
pituitary/hypothalamic disease, tumours
(surgery/radiotherapy to manage)
more of a tertiary adrenal isufficiency
exogenous steroid use
secondary adrenal insufficiency (lack or CRH/ACTH) clinical features
pale skin (no increase ACTH)
aldosterone production intact (regulated by RAS)
SAI treatment
trear w/ hydrocortisone replacement (fludrocortisone unnecessary)
cushing’s syndrome
excess cortisol secretion
high mortality
clinical features of cortisol excess
easy bruising
facial plethora
striae
proximal myopathy
endogenous cause of cushings
ectopic
ACTH independent (too much cortisol) adenoma, adrenal carcinoma
diagnosing cushing’s
establishing cortisol excess
overnight dexamethasone suppression test
24hr urinary free cortisol
late night salivary cortisol
low dose dexamethasone suppression test
repeat to confirm
diagnostic test for cushings syndrome
low dose dexanthesone suppresion ACTH and cortisol measured base line and 24hrs (2mg per day)
what is the commonest cause of cortisol excess
iatrogenic cushing’s syndrome
iatrogenic cushing syndrome happens due to…
prolonged high dose steroid therpay (asthma, RA, IBD, transplants)
chronic suppression of pituitary ACTH production and adrenal atrophy
adrenal suppression
atrophy of adrenal cortex
implications of adrenal suppression
unable to response to stress(illness, surgery)
need extra doses of steroid when ill/surgical procedure
cannot stop suddenly
gradually withdrawal of steroid therapy (if >4-6 weeks)
what are the endocrine causes of hypertension ?
too much aldosterone
too much GH
too much adrenaline and noradrenaline
hypertension and hypokalaemia raises the possibility of…?
primary aldosteronism
primary aldosteronism reflects…
autonomous production of aldosterone independent of its regulators (angiotensin II/potassium)
what appearance would sample have ?
fleshy appearance
what is commonest secondary cause of hypertension
primary aldosteronism (up to 10% of cases, 20% resistant hypertension)
clinical features of primary alodsteronism
significant hypertension
hypokalaemia (in around 30%)
alkalosis
subtypes of primary aldosteronism
adrenal adenoma
(conn’s syndrome)
bilateral adrenal hyperplasia (commonest cause)
rare causes (genetic mutations, unilateral hyperplasia)
diagnosing primary aldosteronism
- confirm aldosterone excess
measure plasma aldosterone and renin and express as ratio (ARR-aldosterone to renin ratio) - confirm subtype
adrenal CT to demonstrate adenoma
sometimes adrenal vein sampling to confirm adenoma is true source of aldosterone excess
management of PA
surgical (only if clear)
- unilateral laparoscopic adrenalectomy
ONLY IF ADRENAL ADENOMA (and excess confrimed in adrenal vein sampling)
- cure of hypokalaemia
- cures hypertension in 30-70% cases
medical
- in bilateral adrenal hyperplasia
- use MR antagonists (spironolactone)
