Adrenal Physiology Flashcards
outline the regulation of adrenal cortisol secretion
outline the affect of cortisol on ADH
cortisol inhibits ADH
why is hyponatremia seen in adrenal insufficiency
- hypovolemia
- when cortisol lowers, it causes an absence of cortisol inhibitory effects on ADH. Relative excess of ADH causes reabsorption of water and the dilution of Na+–> hyponatremia
• In primary adrenal insufficiency, what is the
expected level of ACTH?
high
In central adrenal insufficiency, what is the
expected level of ACTH?
low
• If you have adrenal insufficiency and a normal
ACTH, what can potentially be causing the AI?
normal ACTH= inappropriately low, hsould be high if your cortisol is low. this is a central problem:
hypothalamic issue; mass, infarct/stroke, trauma
pituitary; stalk severing/damage to the axis, mass
Using this diagram, outline where each adrenal gland chemical is released from and what regulates it.
which areas of the adrenal gland is affected with PAI
GFR– the whole cortex. therefore there is a deficiency in aldosterone, cortisol, and sex hormones (testosterone, mainly in women)
which areas of the adrenal gland is affected in CAS
ONLY FR– cortisol and sex hormones. Aldosterone is not afected because its main driver/regulator is the RAAS system of the kidneys. The FR region is regulated by ACTH from the pituitary, so its more affected when the pitutiary or hypothalamus is diseased.
Do you expect hyperkalemia in primary vs.
central adrenal insufficiency?
hyperkalmiea= inability to get excreted. The ENAC- collecting tubule system is not working properly. therefore the glomerulosa area of the adrenal gland not working–PAI.
• In a patient with primary AI, your long term
management would include:
A. GC replacement
B. Mineralocorticoid replacement
C. Medic alert bracelet
D. A & C only
E. All of the above
E
• In a patient with primary AI, your long term
management would include:
A. GC replacement
B. Mineralocorticoid replacement
C. Medic alert bracelet
D. A & C only
E. All of the above
D. dont need glomerulosa (aldosterone) replacement
Do you expect to see skin hyperpigmentation in primary or central adrenal insufficiency?
PRIMARY– primary because ACTH would be really high. ACTH production also produces melanin precursors.
features suggesting corticosteorid insufficiency
glucocorticoid CVS effects
increases contractility of the heart muscle
- increases peripheral vascular tone by augmenting other vasoconstrictor actions
- facilitates catecholamine production and modulation of beta adrenergic receptor synthesis
what kind of shock do you expect in acute adrenal insuffieicny
hypovolemic because of no mineralocorticoids
cardiogenic because of GCs direct effect on heart muscle contractility.
distributive shock due to the decrease in systemic vascular resistance.
main clinical featurse that facor primary over central AI
primary: GFR affected.
- salt craving
- weakness and fatigue because of hyperkalemia
- thin skin
- increase in pigmentation because ACTH is high
- vitiligo
In addition to the GC deficiency symptoms, what other symptoms might make you think of central hypocortisolism?
decrease in sex hormones because ACTH is not present.
- hair thinning, hypogonadism, decreased libido. Not so much the electrolyte disturbances because the MC is still there.
- other symptoms that are cuased by mass affects/hypothalamic disease
A very sick, septic patient in the ICU has a cortisol level of >1000, is this Cushing’s?
no. the person is natrually increased in cortisol because of the acute phase reactanct-ness of it.
best time to measure cortisol if suspecting excess
at night, whne it should be low
best time to measure cortisol if it is suspected to be low
in the morning, when it should be high.
stress that can cause cortisol increase
• Increased ACTH secretagogues: CRH & AVP • Cortisol levels increase at inflammation sites • IL-6 enhances HPA axis response to inflammation • Diurnal variation is lost
• In addition to the 8am cortisol, can you think
of a dynamic way to test the HPA axis to rule out deficiency?
ACTh stimulation test; ACTH infusion should cause cortisol to rise. If it rises, the adrenal galnds are fine but the pit/hypothalamus is the problem. if the cortisol is low, might be primary adrenal insufficiency.
Insulin tolerance test; make the person hypoglycemic– the HPA axis should activate and ACTH levels should be elevated. If not, might be central.
cortisol excess
cushings
aldosterone excess
conns
metanephrine excess
pheochromocytoma
