Adrenal Gland Flashcards
What does the adrenal cortex release?
Mineralocorticoid-aldosterone (Zona glomerulosa)
Glucocorticoids- cortisol (Zona fasciculata)
Androgens- DHEA and androstenedione (Zona reticularis)
What does the adrenal medulla release?
Epi
NE
Dopa
Dopamine
What is the rate limiting step for steroid hormone synthesis?
Cholesterol to pregnenolone which is catalyzed by 20, 22 desmolase
What does the glomerulosa layer of the adrenal cortex lack so it only synthesizes aldosterone?
17 alpha-hydroxylase
What is the major action of aldosterone?
to stimulate the kidney to reabsorb Na and H2O and enhance K secretion @ the distal nephron segments
What do the Fasciculata and reticularis of the adrenal cortex layers lack and what can it synthesize?
lack aldosterone synthase but have 17-alpha-hydroxylase so cortisol and androgen synthesis(DHEA/androstenedione) occurs
How does the cortisol feedback loop work?
High cortisol levels inhibit expression of CRH receptor and ACTH in the coricotrophs of the anterior pituitary
What are the metabolic effects that cortisol has?
Stimulates gluconeogenesis in liver
Enhances protein breakdown in muscle
Stimulates lipolysis
Decreases osteoblastic activity and interferes with Ca absorption in the gut
What anti-inflammatory effects does cortisol have?
inhibits cytokine production
inhibits production of chemo-attractant molecules
Stabilize lysosomal enzymes
Contributes to vasoconstriction and decreased capillary permeability
What immunosuppressive effects does cortisol have?
Decreases lymphocyte proliferation
inhibits hypersenstivity reactions
What receptors are on the adrenal cortex cells for ATCH?
Melanocortin-2 receptor
What is the precursor protein for ACTH and where is it located?
Pro-opiomelanocortin POMC–located in the coricotrophs in the anterior pituitary
When is the highest level of ACTH secretion?
morning hours and diminishes late in the afternoon—corresponds to low glucose level in the morning and want to increase blood glucose levels
What occurs with 21-a-hydroxylase deficiency?
decreased production of cortisol–hypoglycemia/hyperplasia of adrenal gland and aldosterone–loss of salt/hypotension/dehydration
- -Increased ACTH production–no neg feedback–Adrenal hyperplasia
- -increased androgen production–ambiguous genitalia in females
How is 21-a-hydroxylase deficiency diagnosed?
Elevation of 17-hydroxprogesterone before and after ACTH stimulation test
also molecular genetic analysis of CYP21 gene–encodes 21-a-hydroxylase
How is 21-a-hydroxylase deficiency treated?
Glucocorticoids–reduces ACTH levels–decrease hyperplasia and over production of androgens
Mineralocorticoids– used to prevent salt wasting and decreased elevated renin levels
What occurs with 17-a-hydroxylase deficiency?
Reduced cortisol–hyperplasia of adrenal gland and androgen synthesis
Increased cotisterone and aldosterone–HTN and hypokalemia
Reduced estrogen synthesis–sexual infantilism in females
Pseudohermaphroditism and sexual infantilism in males
How is 17-a-hydroxylase deficiency treated?
Glucocorticoid—treat HTN and mineralocorticoid excess
Females–estrogen treatment
Males-surgery/testosterone treatment
What is Cushings syndrome?
Occurs when body’s tissues are exposed to excessive cortisol for long periods of time–excess cortisol of any etiology
What is Cushings dz?
hypercortisolism secondary to excess production of ACTH from a pituitary gland adenoma
What are symptoms seen in Cushings?
Moon face red face upper body obesity increased fat around neck thinning arms and legs osteopenia muscle wasting and weakness increased infections glucose intolerance hypokalemia and HTN
What is a dexamethasone suppression test?
Dexamethasone acts as cortisol and provides negative feedback to the pituitary to suppress the secretion of ACTH
If a pt has an adrenal tumor what will be seen on the Dexamethasone suppression test?
Cortisol-high
ACTH-low
If a pt has an ACTH production tumor what will be seen on the Dexamethasone suppression test?
Cortisol- high
ACTH- high
What is seen in a normal pt who undergoes dexamethasone suppression test?
Cortisol and ACTH both low–the dex is suppressing the ACTH secretion by negative feedback–No ACTH–>no cortisol
What is Addison’s dz?
Hypoadrenal function–failure of the adrenal glands to produce enough cortisol and aldosterone is also deficient in primary adrenal insufficiency
Usually due to autoantibodies against adrenal cells containing 21-a-hydroxylase
What are the symptoms of Addison’s Dz?
Lack of aldosterone–hypotension and hyperkalemia
How is Addison’s Dz diagnosed?
ACTH stimulation– Normal response would be rise in blood and urine cortisol levels
Adrenal insufficiency results in poor response or none at all
CRH stimulation test– Measure cortisol and ACTH in the blood before/after administration
- -Primary adrenal insufficiency- high ACTHs but no cortisol production
- -secondary adrenal insufficiency– deficient cortisol responses and absent/delayed ACTH responses
