Adrenals Flashcards
(36 cards)
which parts of the adrenals make what?
zona glomerulosa (15%) = aldosterone
zona fasciculata (75% of width) = cortisol
zona reticularis (15%) = dehydroepiandrosterone (DHEA)
medulla = adrenaline/NA
brief summary of adrenal steroid synthesis
needs cholesterol
lipoproteins go into adrenocortical cells > mitochondria where it becomes pregnenolone
this leaves to the cortex and diff reactions in diff layers
zones of adrenal cortex - prodcution of their steroids are controlled by what?
G = ECG concentration of K and AngII
F and R = ACTH is trophic to these areas!
what is the HPA axis
corticotrophin releasing hormone from hypothal > anterior pit to release ACTH > adrenal cortex to release cortisol
action of aldosterone
increases ENaC in collecting duct > inc Na absorption, and K excretion > inc BC
**so can cause hypokalaemia!
actions of Ang II
renal: constrict arterioles, inc Na absorption
extra-renal
i. Vasoconstriction systemic - SNS activation
ii. Thirst
iii. ADH release – water retention
iv. Aldosterone release – sodium resorption + potassium secretion
v. Heart remodeling
what is the ACTH stimulation vs secretory ability test
ACTH stimulation: give ACTH i.e. synacthen > measure cortisol
tells you if the adrenals are responding to ACTH
secretory ability tests = central problem
e.g. insulin induced hypoglycaemia, glucagon stimulation, or metyrapone
1’ 2’ vs 3’ adrenal insufficiency
1’ = adrenal cortex problem = MR AND GC deficiency
2’ = pituitary, GC only
3’ = hypothal, GC only
1’ vs 2’ adrenal insufficiency cortisol, ACTH and synacthen results
1’: high ACTH, low cortisol. no cortisol with synacthen. Also will have hypoNa and hyperK, with high renin.
2’: low ACTH, low cortisol. will have cortisol with synacthen.
clinical manifestations of primary adrenal insufficiency
aldosterone deficiency > hypoNa (biggest Sx), hyperK, hypotension, crave salt
cortisol deficiency > hypoglycaemia + ketoacidosis, hypotension
no cortisol -ve FB on pituitary > produces POMC precursor for MSH > hyperpigmentation!
present either acute / chronic (anorexia, fatigue, wt loss etc)
long term Rx for 1’ adrenal insufficiency
- hydrocortisone 10-12mg/m2/day in 3 divided doses, ACTH to monitor
- fludrocortisone 50-150mcg/day - renin to monitor
aetiologies of 1’ adrenal insufficiency
inherited vs acquired:
- CAH (60%) infancy
- AI = addisons 15% child-adol
- TB!! globally
- APS types e.g. APECED
- X-ALD
- drugs / haemorrhage
- genetic causes e.g. abetalipoproteinaemia or Smith-Lemli-Opitx
adrenal crisis - key features
- hypotension, hypoNa, hyperK, hypogly, met acidosis, and non-specific sx
-treat above, and give them hydrocortisone 50-100mg/m2 IV - given fludrocort (florinef) once can tolerate oral fluids
- prevention with stress dose steroids: triple for 3 days, double for 2 days, then normal
key features of ALD
- X linked, ABCD1 gene!! Affects VLFCA transporter > build up in adrenals and brain
3 phenotypes:
- childhood cerebral form: initially like ADHD > actual problems
- adrenomyeloneuropathy - 20s
- addison disease only
inheritance of CAH
AR
key features of the classic CAH
= 21 hydroxylase deficiency (from zona G and F), so you get
1) aldosterone deficiency sx - SEVERE salt wasting
2) cortisol deficiency Sx
3) steroid precursors shafted to zonaR > masculinisation of females, early 2’ sex characteristics
4) the medulla usually develops from high cortisol, so you get weird HR responses
develops at D10-14 of life
key types of CAH
- 21 hydroxylase deficiency (most common)17-beta-hydroxyprog up
- 11 beta-hydroxylase deficiency: 11 deoxycortisol up
- 17-alpha hydroxylase deficiency
- congenital lipoid adrenal hyperplasia = StAR deficiency (worst)
key differentiation between the two most common types of CAH
11-beta hydroxylase will also cause low cortisol, high androgen Sx
BUT the 11 deoxycortisol buildup causes hypertension - high aldo
so present later - preamture adrenarche
key features of 17 alpha hydroxylase deficiency
- lack of this enzyme > no 17-hydroxyprogesterone, which is needed for androgens
- so low cortisol AND low androgens > poorly developed genitals
- aldo pathway doesn’t need it though - so this is active! you’ll get hyPERNa, hyPOK, and hypertension… which will feedback to low aldo
key features of congenital lipoid adrenal hyperplasia
- StAR deficiency - transporter, chol can’t enter
- all aren’t made
- most severe: neonatal insufficiency with all the symptoms
how do you treat classic CAH, and how do you know you’re over or under doing it?
- GC replacement
- overdoing: Cushing’s symptoms
- underdoing: adrenal crisis and androgen excess - fludrocort
- over: HTN, tachycardia, low renin
- under: salt wasting, high renin
comment on height in CAH
even with GC treatment, they get loss of final height of 8-10cm
what is non-classic CAH, and how does it differ from classic CAH?
also cased by 21-OH deficiency
but present AFTER neonatal period with hyperandrogenism e.g. acne, tall advanced bone age, WITHOUT adrenal insufficiency
Cushing’s syndrome vs disease
Cushing’s syndrome – prolonged glucocorticoid excess
Cushing’s disease – Cushing’s syndrome caused by a pituitary adenoma secreting ACTH
