Adrenal Cortex Flashcards
What does the adrenal cortex do?
secretes hormones derived from cholesterol
What is Waterhouse-Friderichsen syndrome
ACUTE primary adrenal insuffienciency due to adrenal hemorrhage associated with Neisseria meningitidis septicemia
what does cholesterol do in the different layers of the cortex
aldo in glomerulosa, cortisol and glucocorticoids in fasiculata, and sex steroids in the reticularis
What is cushing syndrome and what are clinical features? Include mechanisms
excess cortisol muscle weakness with thin extremities moon facies, buffalo hump, and turncal obesity abdominal striae HTN osteoporosis immune suppression amneorrhea
How does excess cortisol cause muscle weakness and moon faceis, buffalo hump, and truncal obesity?
cortisol normally raises blood sugar by breaking down muscles- too much cortisol = muscle breakdown
it also promotes gluconeogenesis (gluconeogenesis = high glucose, which causes excess insulin, which causes storage of fat)
How does excess cortisol cause abdominal striate
cortisol impairs synthesis of collagen
How does excess cortisol cause HTN
upregulates alpha 1 receptors on arterioles, and normally helps maintain vascular tone
How does excess cortisol cause immune suppression?
3 mechanisms:
- inhibitis phospholipase A2. you can’t generate arachidonic acid metabolites, which are needed for inflammation
- inhibits IL-2: important growth factor
- inhibits release of histamine from mast cells (less vasodilation and vascular permeability)
Dx of cushing syndrome
24 hr urine
causes of cushing syndrome. How do you differentiate between them
- exogenous corticosteroids. most common cause. both adrenal glands will become atrophic.
- adrenal problem: adenoma, hyperplasia, or carcinoma. one adrenal will be big, and the opposite adrenal will be atrophic (via ATCH axis)
- ACTH secreting pituitary adenoma: both are big
- paraneoplastic ACTH secretion: classically from small cell carcinoma of the lungs. both adrenals are large.
to distinguish 3 from 4, you should do a high dose dexamethasone test. this is a cortisol analog- it can suppress ACTH production by a pituitary adenoma, but not ectopic ACTH production by small cell lung CA.
follow the effect of this test by following cortisol levels
What is hyperaldosteronism? what does aldo do?
too much aldo
works on late distal region and collecting duct. principle cells grab sodium and dump K in response to aldo.
Alpha intercalated cells dump protons in response to aldo
what are clinical manifestations of hyperaldosteronism?
hypernatremia, hypokalemia, and metabolic alkalosis
HTN (you’ve retained Na)
What are causes of primary hyperaldosteronism? Characteristics of primary hyperaldosteronism?
usually due to adrenal adenoma
sporatic hyperplasia and CA are much less common
see a high Aldo and low renin.
What are causes of secondary hyperaldosternonism? Characteristics?
activation of renin angiotensin system.
classically, in young woman, you can get fibromuscular dysplasia. thickened blood vessel wall decr. blood flow to kidney
or, atherosclerosis in elderly males- also decr. blood flow to kidney
CHF, nephrotic syndrome.
activates juxtoglomerulo apparatus
characterized by high aldo and high renin
What is congenital adrenal hyperplasia
excess sex steroids with hyperplasia of both adrenal glands due to a congenital defect in enzymes necessery for steroidogenesis
biochemistry of congenital adrenal hyperplasia
cholesterol is made into pregmenolone. preg can make mineralocorticoids, cortisol, or sex steroids
you need 21 hydroxylase to make mineralocorticoids and cortisol
with 21 hydroxylase deficiency, you see shunting towards the sex steroids and incr. sex steroids
if XX, you may see cliterol enlargement. if male, you get precocious puberty
also, you see a lack of cortisol: decr. cortisol:
1. life threatening hypotension
2. decr. inhibitory feedback on anterior pituitary. excess ACTH- both adrenals get big in response to excess ACTH
Also, no mineralocorticoids:
no aldo:
1. loose Na and hold K. (hyponatremia and hyperkalemia)
2. hypovolemic
clinical features of congenital adrenal hyperplasia
salt wasting with hyponatremia, hyperkalemia, and hypovolemia
life-threatening hypotension
clitoral enlagement or precocious puberty (I think we learned “ambiguous genitalia” in XX babies)
What is the significance of 11 hydroxylase?
can’t make cortisol, and some shunting towards sex steroids.
however, a patient who has normal 21-hydroxylase can make a weak mineralocorticoid. 11-hydroxylase usually converts this to a stronger mineralicorticoid.
if the patient has classic story for 21 hydroxylase deficiency, but patient doesn’t have salt wasting, hyperkalemia, hypovolemia , it is probably an 11-hydroxylase problem.
What is the significance of 17-hydroxylase?
without it, youc can only produce mineralocorticoids
excess mineralocorticoids, no cortisol, and no sex steroids
you will still have congenital adrenal hyperplasia
adrenal insufficiency: acute
lack of adrenal hormones
acutely: Waterhouse-Friderichsen syndrome
arises in young kid with N. meningitis infection who gets DIC and then gets bilateral necrosis of both adrenal glands. acute lack of cortisol- exacerbates hypotension. looks like a sac of blood adrenal gland.
adrenal insufficency: chronic causes
progressive destruction:
- autoimmune destruction
- TB
- Metastatic carcinoma in the adrenals. Lung cancer loves to go to the adrenals
clinical features of chronic adrenal insufficiency
hypotension, hyponatremia, hypovolemia, hyperkalemia you don’t have aldo.
weakness
hyperpigmentation:
vomiting and diarrhea
Why do we see hyperpigmentation in adrenal insufficiency?
excess ACTH in response to low cortisol levels. ACTH is derived from a molec called POMC. Derivative of POMC is melanocyte stimulating hormone- hyperpigmentation
