Glossary of 2. adrenals
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- The 2 componenets of the adrenal gland are:
- 1. Medulla
- What does ea component produce?
- Medulla: epi/norepi/dopamine
Cortex: androgens, glucocorticoids, mineralcorticoids.
- What are epi/norepi/dopamine known as collectively?
- What causes the release of catecholamines?
- Sympathetic fibers firing in the adrenal medulla.
- What causes the sympathetic fibers to fire and stimulate catecholamines?
- Stress, exercise, hypoglycemia, and trauma.
- How are catecholamines carried through the body?
- Bound to albumin and serum proteins.
- What are the targets of catecholamines?
- Alpha/Beta adrenergic receptors
- Which catecholamine acts on the heart, and how?
- Epinephrine - increases HR and contraction force by acting on beta-adrenergic receptors.
- Which catecholamine acts on blood vessels and how?
- Norepinephrine - constricts BV's and increases resistence and arterial BP.
- What other things do epi and norepinephrine do?
- -Dilate bronchioles
-Increase metabolic rate
-Dilte pupils, inhibit gastrointestinal digestion.
- What is the most common pathology of the adrenal medulla?
- Pheochromocytoma - a benign adenoma in its chromaffin cells
- What is the #1 neoplasm in kids?
- what's a pheochromocytoma often called?
- the 10% tumor
- What methods are used for detecting pheochromocytoma? (4)
- 1. Plasma catecholamines
2. Urine catecholamines
3. Urine metanephrines
4. Urine VMA
- what is VMA?
- Vanillylmandelic acid; the degradation product of norepi and epinephrine.
- What is the degradation product of dopamine?
- HMA - homovanilic acid
- what is another degradation product of epinephrine?
- metanephrine (MN)
- what is another degradation product of norepinephrine?
- normetanephrine (NMN)
- what is the more sensitive test for pheochromocytoma?
- 24-hour urine catecholamines and metabolites.
- What are some tips to remember re: catecholamine specimens?
- -May need >1 24hr urine collecn
-Measure creatinine to ensure that it's a 24 hr urine.
-Don't add a preservative
-Use plasma for better sensitivity than serum
- The catecholamines are amino acid hormones; what is a similar molecule that's more of a neurotransmitter?
- what is serotonin?
- a monoamine neurotransmitter
- what's another name for serotonin?
- 5-HT; 5-hydroxytryptamine
- Where is serotonin made?
- -CNS: In serotonergic neurons
-Intestine: enterochromaffin cells
- what are some important fucntions of serotonin?
- -Sleep regulation
-Smooth muscle releaxation
- what type of tumor is most often related to serotonin?
- Carcinoid tumor - of the small bowel.
- What is 5-HIAA?
- a degradation product of serotonin; measuring both of these in urine will indicate carcinoid tumors.
- What is the adrenal cortex a factory for?
(corticosteroids that is)
- The 4 steroids we're mainly focused on:
- 1. Estrogens
- what are the corticosteroids synthesized from?
- What does aldosterone do?
- Acts on kidney distal tubule; increases Na uptake, K excretion. Increases water resorption
- What is the ultimate consequence of aldosterone?
- Increased extracellular fluid.
- What does cortisol do?
- Increases and maintains normal blood glucose levels.
- How does cortisol work?
- -Mobilizes amino acids/fat
-Stimulates liver gluconeogenesis.
-Suppresses immune system
-Promotes lung maturation and surfactant production.
- What do the androgens do?
- function in sex
- What regulates the adrenal cortex in general?
- But what feedback regulates aldosterone?
- -Increased K
-Angiotensin II due to decr renal blood flow
-ACTH is short-term
- What suppresses aldosterone?
- -High Na
- What is ACTH much more active in controlling?
- What stimulates CHR release?
- Physical and mental stress
- What regulates the androgens partially?
- What is adrenal cortex
- Hypo = Addison's disease
Hyper = Cushing's disease
- How would you differentiate between Primary adrenal insufficiency and ACTH-dependent?
- ACTH primarily controls cortisol, so aldosterone would be less decreased; also ACTH would be decreased in the latter.
- What are the diagnostic levels of Cortisol and ACTH for diagnosing hypofunction?
- Cortisol: <10 ug/dL
ACTH: >250 pg/mL
- and quickly, corticosteroid excess IS?
- MOST COMMON CAUSE OF CUSHINGS:
- exogenous glucocorticoid treatment
- Screening tests for hyperadrenalism:
- -Serum/urine free cortisol
- How would you know if Cushing's disease was ACTH independent?
- -ACTH levels would not be high
-Overnight dexamethasone suppression would not change with high dose.
- So what is the confirmatory test for cushing's?
- Overnight dexamethasone suppression with high dose will show change because the ACTH is so high it STILL stimulates production.
- How does an adrenal tumor affect cortisol, ACTH, and CRH levels?
- -Cortisol is increased
-ACTH is decreased
-CRH is decreased
- What is mineralcorticoid excess?
- What is the name for primary mineralcorticoid excess?
- Conn's syndrome
- How is Conn's syndrome diagnosed?
- By measuring renin and aldosterone levels.
- List 5 assays for assessing adrenal function:
- 1. Cortisol (blood and urine)
5. PRA - plasma renin activity
- What is 17-hydroxyprogesterone?
- the precursor to cortisol
- what is 17-hydroxypregnanolone?
- the precursor to testosterone
- what is progesterone?
- the precursor to aldosterone.
- How is a low-dose Dexamethosone test done?
- 1. Draw baseline blood cortisol
2. Give 1 mg Dexameth at 11pm
3. Draw blood at 8am
- What are the results of lo-dose dexamethosone testing in:
- Normal: <3ug/dl serum, <100ug/dl in urine.
CS: >10ug/dl serum, >120 ug/dl in urine.
- What is high-dose dexamth suppression useful for?
- Differentiating Primary Cushing's (suppression occurs) from 2dary (ACTH stimulated) where no suppression occurs.
- RECAP: for cushing's syndrome,
-What are screening tests?
-What are confirmatory tests?
- Screens: Urine cortisol and lo-dose DM test.
Confirm: Plasma ACTH, serum cortisol, hi-dose DM test.
- What's the principle of the metapyrone stimulation test?
- Inhibiting 11-hydroxylase blocks cortisol synthesis (metapyrone inhibits the enzyme)
- What metapyrone stimulation results are seen in:
- Healthy: cortisol levels drop
Cushing's: ACTH increases.
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