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64 Cards in this Set
- Front
- Back
What is the primary route of excretion of corticosteroids in cats and dogs
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Dogs- Urinary
Cats- Biliary |
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What are 3 main fxns of glucocorticoids
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Affects metabolism
Helps cope with stress Increases renal excretion of H2O |
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What are four ways in which glucocorticoids affect metabolism
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Increase liver gluconeogen.
Decrease peripheral glucose utilization Protein catabolism Increase lipolysis |
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What causes ACTH release from pituitary
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CRH from hypothalamus
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True/False: Cortisol has negative feedback on hypothalamus and pituitary
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True
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What are some fxns of Aldosterone
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Maintain electrolyte balance
Maintain EC H2O volume Increase renal Na retention Increase renal K excretion Increase renal tubular H+ secretion Minor increase in intestinal Na resorption |
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What stimulates secretion of Aldosterone
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High plasma [K+]
Low BP via RAAS Reduced plasma Na via RAAS |
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Which catecholamine is most prevalent in bloodstream
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Epinephrine
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What are the actions of catecholamines
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Vasoconstriction
Increased HR and strength Inhibits GI activity Mydriasis Increased metabolic rate |
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What are 2 causes of naturally occurring cases of hyperadrenocorticism
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PDH (80-85%)
ADH |
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What is PDH hyperadrenocorticism
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Pituitary dependent
Excess ACTH is made by the pituitary |
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What is the typical signalment of a dodg w/ hyperadrenocorticism
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7-9yrs
male= female for PDH female > male for ADH PDH- Mini poodles Dachshunds Bostons Silkies ADH- No real breed predilection, but most are >20kg |
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True/False: The basal cortisol concentration is often normal in cases of hyperadrenocorticism
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True
There is just lack of normal fluctuation of cortisol |
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What percentage of PDH cases have an indentifiable, fxnl pituitary mass
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85-90%
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What is the difference in the pathophysiology as it relates to the adrenal glands b/t ADH and PDH
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PDH- blateral adrenal cortical hyperplasia
ADH- Tumor on one side (usually AC) and atrophy of the contralateral adrenal gland |
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Are most cases of ADH unilateral or bilateral; benign or malignant
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Unilateral
Malignant (only 40% adenomas, the rest AC) |
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What are three mechanisms of excessive cortisol's ability to cause diuresis and polyuria
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Inhibits ADH
Enhances natriuretic factor Increases GFR |
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What causes the pot belly commonly seen with Cushing's
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Protein catabolism induced muscle wasting
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What are the effects of excess cortisol on metabolism
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Breakdown more protein and fat
Increase gluconeogenesis (and cause peripheral insulin resistance) Store more glycogen in liver |
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What is the most common sign seen in Cushing's patients
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PU/PD
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What are 4 reasons for the pendulous abdomen seen with Cushing's
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Large liver
Full bladder More fat there Decreased muscle tone |
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True/False: Only Cushing's patients will have abnormally high adrenal fxn tests
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False
Other illnesses can cause stress and increase cortisol |
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What are the common CBC changes seen in hyperadrenocorticism
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Stress Leukogram
(mature neutrophilia, eosinopenia, lymphopenia) Erythrocytosis |
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Why do you see increased liver enzymes in Cushing's
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ALP- steroid induced
ALT- hepatocytes packed w/ glycogen |
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True/False: Concentrated urine is not compatible w/ a dx of Cushing's
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False
(esp. if in hospital and not drinking much) |
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Why may you see vulva enlargement in hyperadrenocorticism
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Because of weak sex hormones made by the adrenal cortex
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What are some UA findings in hyperadrenocorticism
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Proteinuria (67%)
Bacteriuria (often w/o pyuria or clinical signs) USG < 1.035 often |
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What are three uses for U/S in the dx of Cushings
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Helps tell PDH from ADH if see adrenal tumor (usually)
Identifies which gland is affected Also demonstrates invasiveness |
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What are three main other dzs that can cause adrenal test abnormalities
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Uncontrolled DM
Liver dz Renal failure |
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What is a pro and con for ACTH Stim
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PRO: Most specific (fewest false +s)
CON: Less sensitive then LDDST |
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Why is Dexamethasone used to try to suppress Cortisol in LDDST and HDDST
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It doesn't interfere with the assay being used to tell amount of Cortisol
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What is LDDST's utility
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Good as a screening test
Good sensitivity, but poor specificity (lots of false positives) |
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What signifies a positive LDDST
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Failure to suppress cortisol concentrations to <1 ug/dL at 8 hours
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Why would one do a Urine Cortisol:Creatinine Test
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Good for screening, but not done well enough in this country to stand alone as a way to confirm diagnosis
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What are 4 ways to tell PDH from ADH
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HDDST
Endogenous ACTH U/S Abd LDDST (for ~50% cases) |
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How can a LDDST help tell b/t ADH and PDH (in 50% cases)
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If cortisol has been suppressed to less than 1/2 of baseline after 3-4 hours, it is likely PDH
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Will you see any suppression on HDDST if the hyperadrenocorticism is due to ADH
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NO
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How often will cortisol suppress in PDH patients during a HDDST
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75-85% of the time
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What is more helpful when interpreting HDDST:
suppression or no suppression |
Suppression!
Failure to suppress does not tell for sure b/t ADH and PDH (there are rare cases of ADH that don't suppress), but suppression can only mean PDH |
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Why is it impt to tell b/t ADH and PDH
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Changes tx plan
ADH might be able to be treated surgically, but PDH can only be treated medically |
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Increased cortisol w/ high endogenous ACTH means what
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Likely PDH
Pituitary doesn't care that it is getting negative feedback-- it wants to keep doing its own thing and making ACTH |
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Increased cortisol w/ low endogenous ACTH means what
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Suggests ADH
Pituitary recognizes that it doesn't need to ask adrenals to make more cortisol, but adrenal(s) are fxning autonomously |
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What is the tx for PDH
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Mitotane- kills adrenal cortex
OR Trilostane- inhibits enzymes used to make Cortisol (fewer SEs than Mitotane) |
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What is the first step of tx for ADH
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Medical tx should be attempted first to replace corticosteroids before removing the tumor (since other adrenal gland will be turned off)
Can use: Mitotane Ketoconazole (helps 80% cases) Trilostane (works well but does not shrink mass) |
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What are some SEs encountered w/ Ketoconazole used as a medical tx for ADH
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Hepatotoxicity and Anorexia
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How does the prognosis differ b/t PDH dogs treated w/ Mitotane vs/ Trilostane
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About the same
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What percentage of ADH cases w/ AC have inoperable tumors
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1/2 of the 60% of cases w/ AC cannot be operated b/c invade vena cava or phrenicoabdominal vein
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True/False: The goal of tx for Cushing's is to cure
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False
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What is primary hypoadrenocorticism most commonly caused by
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Immune destruction of the adrenal cortices
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How common in secondary hypoadrenocorticism and what is its cause
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Rare
Pituitary failure causing loss of ACTh production |
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What deficiency(ies) is/are caused by primary hypoadrenocorticism vs. secondary
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Primary- mineralo and gluco
Secondary- gluco only |
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What is the typical signalment of Addison's
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Young adult dogs (4-4.5yr avg)
More commonly female, esp. intact females See more in NM than M |
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What are the two main signs of glucocorticoid deficiency
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Inability to deal w/ stress
Hypoglycemia (weakness and lethargy) |
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What are the 5 main signs of mineralocorticoid deficiency
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Severe Na loss
Hypovolemia K retention leading to hyperK+ Decreased excretion of H+ by kidneys leading to acidosis Excess colonic Na & H2O loss |
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What does hyperkalemia cause
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Negative inotrope
Arrhythmias Usually bradycardia AV Block (first degree progressing to complete) |
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What is the usefulness of a basal cortisol concentration for dx of hypoadrenocorticism
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Won't rule it in, but can rule it out
Also useful, is the ACTH Stim which will show failure of cortisol to increase |
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What are 4 main disturbances you expect to see on chem of Addison's patient
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Na:K <27:1
Hyperkalemia Increased BUN (Pre-renal b/c of hypovolemia) Hyponatremia |
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Why might Addison's be, on the surface, hard to tell from renal failure
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May see increased BUN and Creat, but isosthenuria
USG is variable in Addison's |
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What are hypovolemia's effects on thoracic rads in Addison's patients
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Small heart and great vessels b/c of hypovolemia
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If the basal cortisol level is low, then what
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Do ACTH Stim b/c some normal dogs have low basal cortisol test
But, Sp 98% for <1 ug/dL basal cortisol |
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Explain the therapy for an acute Addisonian crisis
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Correct hypovolemia
Correct electrolytes ACTH Stim Replace gluco and mineralo NPO 24hrs (since many v+) Start tx before get definitive dx |
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What are two drugs used to replace mineralocorticoids long term
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Fludrocortisone PO
Injectable DOCP |
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What is used to replace glucocorticoids long term
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Oral Prednisolone
Can withdraw Pred in many on Fludrocortisone b/c it, too, has gluco activity But, those on DOCP must stay on Pred b/c DOCP has no gluco activity |
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What is the px for hypoadrenocorticism
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Excellent
Normal life span But, must give meds and can be very expensive for lg dogs |