Endocrine (Clin Path)

TRH - TSH - T4 and T3

T4 is produced by thyroid glands
T3 produced from T4 inside cells
T3 produced from T4 inhibits secretion of TSH from pituitary

throglobulin stored in follicular lumina

diurnal variation
highest in horses late in the afternoon

false

mostly bound to plasma proteins

metabolic rate
O2 consumption
Heart Rate
Bone reformation and resorption
Catabolism of muscle and fat
Protein syntheisis
Erythropoiesis

hyperthyroidism = adenoma
hypothyroidism = adenocarcinoma
rare

90% will have increase T4

measure sera if it is greater than upper reference limit (free T4)

most common canine endocrinopathy

see lymphocytic thyroiditis (immune mediated)
idiopathic thyroid atrophy

measure total t4 and free t4
measure endogenous TSH
measure thyroglobulin autoantibody testing

variable

greater than 1 year
no increase in appetite with weight gain
unwilling to exercise
hyperkeratosis
endocrine alopecia
myxedema

milk normocytic, normochromic, non regenerative anemia

fasting hypercholesterolemia

fasting hypertriglyceridemia

illness that may cause a decrease in T4 by the thyroid


can be caused by drugs
-glucocorticoids
-phenobarbital
-Sulfonamides
-Furosemide

PTH regulates blood calcium and blood phosphorus

70% of cats have hyperthyroid

see hyperphosphatemia and low ionized calcium

rule out hypothyroidism and test for hyperadrenocortisism (cushings)

Euthyroid sickness

is often a secondary problem

hypoparathyroidism

Deficiency of ADH

no response to ADH

pyometra, liver failure, hypo and hyperadrenocorticism, pyelonephritis, hypokalemia, hyperthyroid, acromegaly,hypercalcemia
drug induced

demopression
modified water deprivation test

cushings syndromes

common

clinical sugns are caused by persistenc cortisol secretion

many patient do not have increase cortisol
-basal cortisol NOT a useful test
episodic exaggerated secretion
mild but continuously increase secretion

iatrogenic - high doses of glucocorticoids

pituitary adenoma - 85%
funtional adrenal tumor 15% of cases

middle aged greater than 6 years old
60% female
slowly progressive
PU/PD
heat intolerance, panting
polyphagia
lethergy
alopecia
pyoderma
cutaneous hyperpigmentation
fasting hyperglycemia
anestrus
testicular atrophy
exophthalmos

poodles
german shepards
dachshunds
labs
terriers

Stress Leukogram
increase in ALT, ALP and Cholesterol
SpG high
urinary tract infections (peylonephritis)

confirmatory test

Give dexamethasone and see if you get respnse (supprestion) of cortisol production)

Take a blood sample be fore and at 4 and 8 hours to check levels of cortisol
Levels decrease

If cortisol is not suppressed, most likely adrenal based
If cotrison is suppresed at the 4 hour but then high at the 8 hour most likely at the pituitary level (secreting tumor


If suppress the animal is fine

confirmatory test

after 1 hour after the test normal dof should have a cortisol between 4-10 micrograms/decaliter

if animal is above the upper limit - hyperadrenocortisism

below the lower limit are hypoadrenocorticism or its iatrogenic

can not distinguish between pituitary and adrenal origin

seen in female dogs (70%)
young and middle aged greater than 5 years
mixed breeds most prevalent
Great Danes, poodles

Primary- immune mediated destruction of adrenal cortices (main cause)

secondary - destructive lesion in hypothalamus or pituitary

signs related to lack of aldosterone
-hypovolemic and lack of Na
-hyperkalemic
-acidosis

poor appetite/anorexia
lethergy
vomiting
thinness
weakness

dehydration
weak pulse
weak femoral pulse
hypothermia

ACTH stim

no response is hypoadrenocorticism

mild - moderate, normocytic, normochromic non regenerative anemia

dehydration effect on PCV

if animal is in addisonian crisis, rehydration can dilute RBCs to life-threatening levels

sicks and stressed animal expect stress leukogram but generally WON"T find one