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Clinical Chemistry > Adrenal gland > Flashcards

Adrenal gland Flashcards

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1
Q

cellular zonation of adrenal cortex

A

zona glomerulosa - mineralcorticoids (aldosteron)
zona fasiculata - glucocorticoids (cortisone, corisol, corticosterone)
zona reticularis- sex hormones (androgens, estrogens)
chromaffin cells - catacholamines ( NE & EPI)

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2
Q

Adrenal gland general function

A

affect blood pressure & electrolytes within the blood

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3
Q

Adrenal regulation

A

hypothalamus - CRH
pituitary gland - ACTH
adrenal cortex- cortisol feedback loop

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4
Q

precursor for adrenal gland hormones

A

cholesterol!

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5
Q

cortisol feedback mechanism

A

hypothalamus –(CRH)–> anterior pituitary –(ACTH)–>adrenal cortex–> cortisol!
cortisol inhibits hypothalamus & anterior pituitary

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6
Q

zona glomerulosa (outer 10%)

A

mineralcorticoids
aldosterone - enzyme aldosterone synthetase active
stimulated by ACTH & renin axis system

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7
Q

zona faciculata (middle 75%)

A

glucocorticoids - cortisol, cortisone, DHEA

stimulated by ACTH

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8
Q

zona reticularis (inner 10%)

A

androgens like DHEA are sulfated to DHEAS (main androgen)

stimulated by ACTH

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9
Q

Renin-angiotensin system (RAS)

A

renin is released from kidney juxtaglomerulus apparatus
renin acts on angiotensin-ogen from liver to get angiotensin I
angiotensin I is converted by ACE (lung) to angiotensin II ( vasoconstrictor)

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10
Q

what does Renin-angiotensin system (RAS) lead to in the body?

A

aldosterone release from adrenal cortex & resulting absorption of Na+ from the proximal tubule of the kidney
& increase in osmotic pressure & improvement of blood pressure

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11
Q

cortisol general

A

made in F-zone w/ adequate 17-alpha-hydrolase activity
dinural variation - regulated by ACTH
90% protein bound (CBG)

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12
Q

cortisol effects

A 
stimulates gluconeogensis & glycogenesis
decreasing protein synthesis
increase blood glucose
decrease calcium absorption
increases adipose fat tissue
influences CNS pain perception & sense of well being
slows inflammatory response
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13
Q

cortisol & ATCH diurnal cycles

A

lowest at midnight & highest around 8 am

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14
Q

adrenal insufficiency labs show:

A

decreased cortisol
increased ACTH & CRH
the increased ACTH leads to adrenal gland hyperplasia & increased androgen production

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15
Q

Diseases associated with aldosterone

A

congenital adrenal hyperplasia
isolated hypoaldosteronism
hyperaldosteronism

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16
Q

diseases associated with cortisol

A

addison’s disease

cushings syndrome

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17
Q

Congenital adrenal hyperplasia

A

inherited family of enzyme disorders
lead to decreased cortisol & decreased aldosterone
defect in 21-hydroxylase enzyme & causes a build up of 17-hydroxy progesterone & androgens bc cortisol is low
treat with replacement cortisol

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18
Q

isolated hypoaldosteroneism

A

only aldosterone is decreased
see in adrenal gland destruction, chronic heparin therapy etc
patients with diabetes, mild metabolic acidosis, increased metabolic acidosis & elevated serum K+ with low urinary K+

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19
Q

hyperaldosteronism

A

excess aldosterone
may develop metabolic alkalosis, hyper-tension & increased serum K+
determine PA/PRA (plasma aldosterone/plasma renin activity)
PA/PRA >25 indicative for disease

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20
Q

urinary excretion of K+ suggests:

A

hyperaldosteronism

especially >30 mEq/L

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21
Q

upright PA/PRA ratio (>25)

A

hyperaldosteronism

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22
Q

no Captopril suppression suggests:

A

hyperaldosteronism

23
Q

Cortisol insufficiency

A

addisons disease
decrease cortisol w/ weakness, fatigue, anorexia, diarrhea, nausea
often 90% of cortex gland is destroyed

24
Q

lab values for addison’s disease

A

decreased Na+, glucose, cortisol
increased K+, ACTH, calcicum
prerenal azotemia
mild metabolic acidosis

25
Q

causes of addisons

A

autoimmune (70%)

infections (tuberculosis 20%), hemorrhage, infiltrative processes, metastasis

26
Q

cortisol insufficiency testing

A

when decreased cortisol w/ increased ACTH on 8 am specimen - need stimulation tests

27
Q

Cosynthopin

A

stimulates both cortisol & aldosterone secretions

look for rise in cortisol when given 250 ug

28
Q

Metyrapone

A

give at midnight, blocks 11-B-hydroxylase & look for rise in 11-DOC while cortisole decreases

29
Q

normal response to cosynthopin but not to metyrapone?

A

look for secondary adrenal insufficiency (ACTH secreting tumor)

30
Q

Addison’s disease general

A

primary adrenal insufficiency - gradual destruction of adrenal gland
90% loss before symptoms
secondary adrenal insufficiency- most common form of the disease; Lack of ACTH

31
Q

Cushing’s syndrome general

A

prolonged exposure to high levels of cortisol
leads to glucose problems, immune suppression & depression
high cortisol & low ACTH if primary

32
Q

common causes of cushings

A

ACTH secreting pituitary adenoma (68%)
autocortisol production by adrenal tumor (17%)
excess ectopic ACTH or CRH production (15%)

33
Q

Assay methods

A

2 site IRMA assay for ACTH

ELISA for cortisol

34
Q

how to separate ACTH-dependent from ACTH-independent cushings syndrome

A

ACTH dependent cushings: ACTH >15 pg/uL & cortisol >15 ug/L

35
Q

Cushing’s syndrome symptoms

A

upper body obesity: round face, increased fat about neck, thinning of arms & legs
fragile skin: easy bruising etc
hypertension & diabetes (!!!)- secondary diabetic condition
excess hair growth & fertility issues

36
Q

Cortisol Suppression testing w/ Dexamethasone

A

differentiates between pituitary & ectopic ACTH secreting tumor
pituitary is 90% suppressed but tumor is not!!

37
Q

Cushing’s lab testing

A

excess cortisol, LOSS OF DIURNAL VARIATION, resistance to suppression test
urine free cortisol levels on 24 hr urine
serum cortisol @ 8 am & 4 pm

38
Q

DHEA & DHEAS

A

formed in zona reticularis (cholesterol based) & are precursors to number of androgens: androstenedione, testosterone, 5-dehydrotestosterone (5-DHT) & estrogens
men get 5% of their testosterone from adrenal gland
women get 40-65% of their testosterone from the adrenal gland

39
Q

Androgen excess

A

overproduction can lead to infertility & masculization in women
over production inhibits pituitary gonadotropin hormone production leading to loss on needed hormones

40
Q

adrenal release of cortisol occurs when the pituitary releases?

A

ACTH

41
Q

aldosterone is synthesized in the adrenal cortex layer____?

A

zona glomerulosa

42
Q

Catecholamine synthesis location

A

adrenal medulla

43
Q

Catecholamines (2)

A

epinephrine & norepinephrine

44
Q

Epinephrine

A

made form tyrosine (!)
increases cardiac output, blood pressure
direct blood to muscles & brain
mobilizes fuel from storage to action

45
Q

rate of norepinephrine to epinephrine

A

9:1

46
Q

enzyme that converts norepi to epi

A

phenylethanolamine N-methyl transferase or PNMT

this is the control point in epinephrine synthesis

47
Q

epinephrine cell action

A

interacts with alpha-adrenergic receptors on cells that cause a cascade of events on the interior of the cell
produce more ATP etc

48
Q

Catecholamine degradation

A

3 mechanisms:

  1. reuptake into secretory vesicles
  2. uptake in nonneuronal cells (mostly liver)
  3. degradation through 2 enzymes lead to formation of metanephrine & VMA from free catecholamines
49
Q

2 enzymes that produce metanephrine & VMA from free catecholamines

A

catechol methyl transferase or COMT

monoamine oxidase MAO

50
Q

methods of analysis of catecholamines

A

HPLC, fluorometric methods, or LC-MS/MS
used for urinary 24 hr metabolites of catecholamines
reliable & not altered by age/gender
drugs can interfere with fluormetric methods

color methods - test VMA
special urine collection, NO BANANAS or VANILLA up to 3 days prior

51
Q

causes of sympathetic hyperactivity

A 
elevated epinephrine
autonomic dysfunction
panic attacks
stress response
drugs
food with tyramine
PHEOCHROMOCYTOMA
52
Q

Pheochromocytoma

A

tumor of chromaffin cells

hypertension present, high levels of catecholamines & will NOT be suppressed by CLONIDINE

53
Q

testing for pheochromocytoma

A

24 hr urine test for metanephrines (!) & catecholamines

clonidine (should suppress epinephrine) suppression test is 92% accurate

Clinical Chemistry (23 decks)

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