Endocrine/Metabolic/Nutrition Flashcards
The most common cause of DI is what category polyuric disorder?
secondary nephrogenic DI
How does hypokalemia cause Pu/Pd?
Causes downregulation of AQ-2 and may alter medullary interstitial gradient by downregulating urea transporters. Also might interfere with AVP release from pituitary
How does polycythemia cause pu/pd?
Abnormal AVP response due to increased blood volume/hyperviscosity stimulating ANP from baroreceptors, thus inhibits AVP release
Dogs can still have Pu/pd despite having the ability to concentrate urine. T/F?
True - consider osmotic diuresis, psychogenic polydipsia, and disorders in AVP secretion (note - this generally would still result in non concentrated urine however)
Serum Na concentrations in the higher range and a USG of 1.003 is more consistent with DI or psychogenic polydipsia?
DI
Hypophysectomy always results in permanent CDI. T/F?
False - sufficient hormone can be released from fibers ending in median eminence and pituitary stalk (unless that’s removed too). Most dogs can be weaned off DDAVP.
Why could primary nephrogenic DI dogs be responsive to DDAVP?
The V2 receptors may have an extremely low binding affinity for AVP, requiring higher doses than physiologically produced
Giving DDAVP to a dog with pituitary dependent HAC will result in no improvement, transient improvement, or complete improvement?
Transient improvement. (Dogs with pituitary dependent HAC can respond similar to dogs with partial CDI or psychogenic polydipsia)
When is the earliest one can evaluate response to DDAVP?
5-7d, because renal medullary wash out may complicate concentration
What % change in USG indicates response to DDAVP consistent with CDI?
50% change. Or USG > 1.030
When to end a modified water deprivation test?
Lost 3% of body weight, USG > 1.030, clinical dehydration, behavior/mentation change (due to dehydration), azotemia, hypernatremia. Can do plateau of urine concentration (change of less than 5% or 30 mOsm/kg of water over 3h) but this can have a false plateau
Giving DDAVP to a dog without DI will result in what change to USG during water deprivation test?
Little effect.< 10 % change.
Diagnosis for complete central DI with a modified water deprivation test?
Minimal (<10%) change in USG at 5% dehydration. Increase in 50% of USG or urine osmolality with DDAVP.
A dog that is clinically dehydrated with a USG <1.030 does not have psychogenic polydipsia. T/F?
False - can still be <1.030 due to medullary solute washout
Detecting hypertonic dehydration is soonest detected with what hydration parameter?
Body weight.
Free water deficit formula
(([Current Na] / [normal Na]) - 1 ) * (.6 * kg)
In differentiating DI between psychogenic polydipsia, a low plasma osmolality is consistent with which process?
Psychogenic polydipsia
Diagnosis of syndrome of inappropriate ADH?
hyponatremia with plasma hypoosmolality; inappropriately high urine osmolality with plasma hypo-osmolality; normal renal and adrenal function; presence of natriuresis with hyponatremia; inappropriately AVP with plasma osmolality; no hypovolemia/edema/ascites; correction of hyponatremia with fluid restriction
Popular breed in which pituitary dwarfism is known?
German Shepherd
Difference in growth for pituitary dwarfism vs congenital hypothyroidism?
Pituitary dwarf - proportionate
Hypothyroid - disproportionate (short limbs, broad head)
Basal growth hormone assays are not useful to distinguish pituitary dwarfs from normal dogs. T/F?
True
What is the gene mutation present in GSDs responsible for pituitary dwarfism? (And can be screened for)
- ABCD1
- LHX3
- MCH3
- SLC2A9
LHX3 gene mutation
Measurement of what hormone is used to dose adjustments of porcine GH to pituitary dwarfs?
IGF-1
What other congenital abnormality accompanies pituitary dwarfs and should also be treated?
Hypothyroidism
Prognosis if pituitary dwarf left untreated?
Severe hair coat and skin abnormalities; become progressively thin, lethargic, dull. Die or euthanized between 3-5 years of age.
If treated- live several years with good QOL but still do not have normal life expectancy
What is cause of acromegaly in most cats?
GH-producing pituitary adenoma
IGF-1 can be falsely low in an acromegalic cat in what scenarios?
serious other concurrent disease, untreated diabetic cat, grey zone IGF, starvation, early acromegaly
IGF-1 can be falsely high in a normal cat in what scenarios?
Vigorous or long-term insulin treatments, problems with assay
What is generally used for medical management for acromegaly?
Pasireotide (somatostatin)
Cabergoline (dopamine agonist)
what are differentials for acromegaly in a dog?
Excess progesterone production or administration (intact females), pituitary tumor is very rare
Which body system is most commonly affected in dogs with diagnosed with hypothyroidism?
Skin (60-80%)
Why is T4 measured instead of T3?
T4 is produced only by thyroid, while T3 can also come from extrathyroidal sites through the deiodination of T4.
What dog type has a lower tT4 and fT4 than other breeds?
Sighthounds (Greyhound, Whippet, Saluki, Sloughi)
What percentage of hypothyroid dogs have TSH within the reference range?
20-40%
A more useful test of thyroid function in Greyhounds would be
total T3 - generally within normal reference range and thyroiditis is not common
If you are suspicious that a dog is not hypothyroid but is receiving supplementation, how soon should you recheck thyroid levels after stopping supplementation?
Recheck in 6-8w ideally. Earliest re-evaluation in 4w. (however JVIM 2017 said that in dogs receiving levothyroxine SID for 16w you can recheck as early as 1 week)
If you receive a post-pill T4 taken 5 hours after medication that is in lower half of reference range in a hypothyroid dog whose clinical signs are well-controlled, what is the the gold standard next step?
Measure serum TSH - if normal - maintain dose.
Starting thyroid doses in dogs with cardiomyoopathy should be what % of the normal dose?
25-50%
Dogs with severe malabsorptive disease may benefit from what medication instead of levothyroxine? What are disadvantages of this medication?
Liothyronine. Has to be dosed three times a day and must measure T3. (2-4h post). Higher risk of toxicosis.
95% of cats that are hyperthyroid are diagnosed over what age?
8 years
fT4 is more sensitive/specific than tT4 but is less sensitive/specific in cats for detection of hyperthyroidism.
Sensitive, specific
What is the significance of measuring T3 in a T3 suppression test in measurement of feline hyperthyroidism?
T3 should ALWAYS reliably increase if done correctly. If T3 is not increased, then owner was not compliant and test results may not be reliable.
Where else does can pertechnetate accumulate besides thyroid glands during thyroid scintigraphy (if any)?
Salivary glands and gastric mucosa
The majority of hyperthyroid cats have bilateral or unilateral disease?
Bilateral (70%) according to Nelson/Feldman
Advantage of thyroid scintigraphy over CT scan?
Can distinguish unilateral vs bilateral dysfunction and can identify ectopic tissue
Why is medical management recommended prior to definitive treatment for hyperthyroidism?
Assess for development of azotemia
Prescription y/d may be acceptable for cats with what other concurrent disease process?
Early renal disease (at least…as of time of Nelson Feldman 4th edition)
Thyroid carcinomas most frequently metastasize to which site in the dog?
Lungs (77% of metastasized tumors)
What % of dogs had had evidence of metastasis with thyroid carcinomas with tumor volume of > 100 cm^3?
100%
Describe a clinical case of thyroid carcinoma in a dog for which surgery would be treatment of choice.
Freely moveable, non-invasive thyroid tumors (25-50% of dogs)
PTH encourages Ca reabsorption from which part of the tubule?
Distal tubule
Adult onset hyperparathyroidism is most well known noted as an inheritable condition in what breed of dog?
Keeshond
How does acid-base affect ionized calcium concentrations?
Acidosis decreases plasma protein-binding affinity for calcium > ionized hypercalcemia Alkalosis has the opposite effect
Ca x P product over what number is concerning for nephrotoxicity.
Depends on source, but around 60-80
Hypocalcemia will cause increase nerve cell membrane permeability to sodium. This will result in increased or decreased excitability?
Increased. (Hence why tetany and seizures can be caused by hypocalcemia)
Why is magnesium a cofactor for PTH secretion?
Required for release of stored hormone from secretory granules
What are adverse effects of methimazole in cats?
Anorexia, vomiting, lethargy, ulcerative pinnal lesions, blood dyscrasias, hepatopathy, rarely myasthenia
Calcium levels for supplementation for dogs with hypoparathyroidism should: a. just below reference range b. lower half of reference range c. upper half of reference range d. just over reference range
a. just below (according to nelson/feldman) as this should not induce clinical signs, maximize PTH secretion (if present), and avoid the possibility of excess calcium (and causing nephrotoxicity or cystoliths through calciuria)
Stress-induced hyperglycemia can take several days to resolve in a diabetic animal. T/F?
True
Human portable glucometer will generally underestimate/overestimate blood glucose in dogs.
Underestimate
Anti-insulin antibodies in dogs can develop if insulin is developed from which sources?
Canine or beef
Mechanism of action of glipizide? (oral hypoglycemic most often used in cats and studied the most)
Sulfonylurea- stimulate insulin secretion
If used, acarbose seems to have its best effects in cats that have to remain on a high carbohydrate diet.T/F?
True
Mechanism of action of exenatide.
GLP-1 agonist. (enhance insulin secretion, reduce glucagon secretion, reduce post-prandial hyperglycemia, slows gastric emptying, enhances satiation). Can be given once a week in XR models
Fructosamine can be falsely low under what pathological situations in cats? (and dogs)
Hyperthyroidism, hypoalbuminemia
What does Nelson/Feldman recommend for diabetic ketosis patients (with no acidosis)?
Short acting insulin TID (with feedings at each meal) until ketosis resolves, then long-acting insulin…
Concurrent causes for dogs/cats in HHS?
Sepsis, hemorrhage, anemia, pulmonary disease, liver disease, kidney disease!, panc, CHF
Differences in treatment for HHS vs DKA?
Heavier emphasis on fluid therapy for HHS. Insulin doses are started lower (Nelson/Feldman recommends 50% lower) to also avoid rapid changes in glucose affecting osmolality and neurologic status
Most common sites of beta cell metastasis?
regional lymphatics and lymph nodes of liver and peripancreatic omentum (pulmonary is not until late in disease)
Glucose enters beta cell by what transporter?
GLUT-2
Hepatic glucose production is inversely related to what concentration?
Blood glucose
What can set off clinical signs in dogs with insulinoma?
Increased exercise, fasting, excitement, eating (especially highly digestible food)
A Maltese that presents for weakness has hypoglycemia, increased liver enzymes, and hepatomegaly with severe vacuolation noted on liver aspirate. What is your top differential?
Glycogen storage disease (Type Ia). Other types - Type II - Lapland dogs; Type III - GSD and Curly Coated Retrievers, Type IV - Norwegian Forest Cats.
Insulin levels in the lower half to below the refence range rule out insulinoma. T/F?
False - only if insulin is below the reference range
Mechanism of action of diazoxide? What else can be given with it to potentiate its effects?
Benzothiadiazide diuretic that inhibits insulin secretion, stimulates hepatic gluconeogenesis and glycogenolysis, and inhibits tissue use of glucose. No anti-neoplastic effects. Can be used with thiazide diuretic (hydrochlorothiazide).
Side effects of streptozocin?
Many. Nephrotoxicity, hepatopathy, diabetes mellitus, GI signs.
The stepwise medical recommendation for insulinoma?
Small frequent feedings (ideally higher fiber/carb) > steroids > diazoxide > somatostastin/streptozotocin
the ACTH stim is more sensitive to detect PDH or adrenal tumor?
PDH