Endocrine Flashcards
What at the two hormones synthesized and secreted by regulation of TSH?
T4 (Thyroxine)
Triiodothyronine (T3)
What hormone is 100% synthesized by the thyroid?
Thyroxine (T4)
What are the thyroid hormone effects?
Increase metabolic rate Increase oxygen consumption, stimulates erythropoiesis Positive inotrope Positive chronotrope Catabolize muscle & adipose tissue Alters lipoprotein metabolism
What are the Thyroid function tests?
Total Thyroxine (T4) Free Thyroxine (FT4) Thyroid stimulating hormone (TSH)
What does a Dog Thyroid Panel include?
TT4
Free T4
TSH
What does a Cat Thyroid Panel include?
Total T4
Free T4
What does Total T4 measure?
total circulating T4 (Protein bound and free)
What are the 2 common assays for measuring Total T4?
Radioimmuuunoassay
Snap ELISA test kit
What does Free T4 measure?
unbound circulating T4
What are the 2 common assay to measure Free T4?
Equilibrium Dialysis
Radioimmunoassay
What 3 assays measure TSH?
Immunoradiometric
Chemiluminescent
ELISA
Which test is the gold standard for measuring Total T4?
Radioimmunoassay
What is the most common cause of Canine Hypothyroidism?
Lymphocytic Thyroiditis
What are the clinical signs of Hypothyroidism?
Fat Lethargy Weight Gain Skin lesions Bradycardia Hypothermia
What three things cause secondary hypothyroidism?
Neoplasia
Congenital malformation
Trauma or surgery
What hormone is not sythesized with secondary hypothyroidism?
TSH
What are the diagnostic clinical signs seen?
nonregenerative anemia Hypercholesterolemia hypertriglyceridemia Decreased Total T4 Decreased Free T4 Increased TSH
What are the diagnostic clinical signs for secondary hypothyroidism?
decreased total T4
decreased Free T4
decreased TSH
Euthyroid Sick Syndrome
Decreased Total T4
Absent clinical signs of hypothyroidism
TSH IS NORMAL!!
What else can cause euthyroid sick syndrome?
Glucocorticoids
Sulfonamides
Decreased Total T4
Increased TSH
Primary hypothyroidism
Increased TSH
Early hypothyroid?
Decreased Total T4
Decreased Free T4
Decreased TSH
Secondary Hypothyroidism
Decreased Total T4
Sometimes decreased Free T4
Euthyroid Sick Syndrome
Does a Canine Thyroid Carcinoma exhibit signs of abnormal thyroid function?
NO
What is the most common chemistry abnormality in hypothyroid dogs?
Hypercholesterolemia
What is the most common endocrine disorder of cats?
Hyperthyroidism
What is the pathogenesis of hyperthyroidism in cats?
Functional adenoma (Hyperplasia) thyroid adenocarcinoma
What are the clinical signs of hyperthyroidism in cats?
Tachycardia Polyphagia Weight loss Hyperactivity Diarrhea Palpable Thyroid slip
What are the diagnostic clinical signs of hyperthyroidism in cats?
Polycythemia Heinz body fromation Stress Leukogram Increased liver enzyme activity (ALT) Azotemia - Dehydration and renal insufficiency
What is masked in Hyperthyroid cats?
Azotemia due to increased GFR
What is increased in Hyperthyroid cats?
Total T4
What is a common chemistry abnormality in hyperthyroid cats?
Increased Liver Enzyme Activity
What is the most reliable thyroid function test for hyperthyroid in cats?
Total T4
What do Chief Cells synthesize and secrete?
Parathyroid hormone
What is the function of Parathyroid hormone?
Increased plasma Calcium
Decreased plasma phosphorus
What stimulates PTH secretion?
Decreased Calcium
What inhibits PTH secretion?
Increased Calcium
What conditions cause decreased PTH?
Calcitriol
Hypomagnesemia
Hypophosphatemia
What condition increases PTH?
Hyperphosphatemia
What does PTH promote?
Calcium resorption from the bone
Renal resorption of calcium
Formation of active Vitamin D
Increased Calcium resorption from intestine
What does PTH inhibit?
Phosphorus resorption by the kidney –> increased phosphorus secretion in urine
What are the two disease of the Parathyroid gland?
Primary hyperparathyroidism
Hypoparathyroidism
What are the two causes of hypoparathyroidism?
Lymphocytic parathyroiditis
Iatrogenic
What causes Primary Hyperparathyroidism?
Parathyroid Adenoma
What on a chemistry panel can diagnose Parathyroid disease?
Total Calcium
Ionized Calcium
Phosphorus
What endocrine test can confirm parathyroid disease?
Parathyroid Hormone Measurement
What does a Parathyroid adenoma produce?
PTH
What changes do you see on a chemistry panel with Hyperparathyroidsim?
Hypercalcemia
Hypophosphatemia
Normal to Increased PTH
What are the other causes of hypercalcemia?
D - Vitamin D Toxicosis R - Renal Failure A - Addison's Disease G - Granulomatous Disease O - Ostelytic Disease N - Neoplasia S - Spurious H - Hyperparathyroidism I - Idiopathic, Iatrogenic T - Temperature, Toxins
What causes Hypoparathyroidism?
Decreased production of PTH
What changes in the chemistry panel do you see with Hypoparathyroidism?
Hypocalcemia
Hyperphosphatemia
Normal to decreased PTH
What hormones does the Adenohypophysis produce?
ACTH Somatotropin (GH) MSH TSH FSH LH Prolactin
What does the Neurohypophysis produce?
ADH/Vasopressin
Oxytocin
What does ADH/Vasopression?
Water resorption in the kidney through aquaporins
What are the two types of Diabetes?
Central
Nephrogenic
What is deficient in Central Diabetes Insipidus?
ADH production
What is wrong in Nephrogenic Diabetes Insipidus?
No response to ADH
What are the clinical signs of Diabtetes Insipidus?
PU/PD
Low Urine SpGr
What is the primary differential diagnosis for Diabetes Insipidus?
Psychogenic Polydipsia
What are the three tests that differentiate between Central DI and Nephrogenic DI?
Water Deprivation Test
ADH Response Test
Modified Water Deprivation Test
What types of animals do you NOT perform the water deprivation test on?
Azotemic
Dehydrated
Suspected of Renal Disease
What is the diagnosis if the urine is concentrated after the water deprivation test?
Pyschogenic Polydipsia
If the urine remains dilute after the water deprivation test what is the diagnoses?
Central Diabetes Insipidus
Nephrogenic Diabetes Insipidus
What test is used to differentiate Central from Nephrogenic Diabetes Insipidus?
ADH Response Test
If the Urine concentrates after the ADH Response test what is the diagnosis?
Central Diabetes Insipidus
If the urine DOES NOT concentrate after the ADH Response test what is the diagnosis?
Nephrogenic Diabetes Insipidus
What is Central Diabetes Insipidus characterized by?
Decreased ADH
PU/PD
Low USG
What is Nephrogenic Diabetes Insipidus caused by?
Hypercalcemia
Drug induced: Glucocorticoids, halothane, nethoxyflurane, ethanol
Disease States: Pyometra, liver failure, etc
Which disease is associated with interference at the level of the ADH receptor?
Nephrogenic DI
What is the common name for Canine Hyperadrenocorticism?
Canine Cushing’s Syndrome
What are the three forms of Hyperadrenocorticism?
Pituitary-dependent hyperadrenocorticism
Function adrenal tumor
Iatrogenic
What are the clinical signs of Hyperadrenocorticism?
PU/PD Pot-bellied Panting Muscle Weakness Ligament Weakness Alopecia Calcinosis cutis Cutaneous hyperpigmentation
What are the Laboratory abnormalities seen with Hyperadrenocorticism?
Stress Leukogram Increased ALP Increased ALT Increased Cholesterol Low Urine SpGr UTI
What are the screening tests for Hyperadrenocorticism?
ALP Activity
Urine Cortisol: Creatinine ratio
What are the confirmatory/diagnostic tests for hyperadrenocorticism?
Low Dose Dexamethasone suppression test (LDDST)
AST Stimulating Test
What are the differentiating tests for hyperadrenocorticism?
Low Dose Dexamethasone suppression test (LDDST)
High Dose Dexamethasone Suppression test (HDDST)
Endogenous ACTH measurement
Imaging
What is frequently increased with hyperadrenocorticism?
ALP
If the Urine Cortisol: Creatinine ratio is increase……
The patient has hyperadrenocorticism
If the patient has a pituitary tumor with the LDDStest….
Cortisol production is not suppressed
If the patient has an adrenal tumor with the LDDStest…
Cortisol production is NEVER supressed
How do you interpret the LDDStest?
If decreased at 8 hours then the patient is Normal
If increased at 8 hours then the dog has not suppressed - hyperadrenocorticism
Step 2:
If increased at 4 hours - hyperadrenocorticism
If decreased then the dog has suppressed: PPDH
What is the only test that will identify iatrogenic hyperadrenocorticism?
ACTH Stimulation Test
How do you interpret the ACTH Stimulation test?
Dogs with hyperadrenocorticism hypersecrete cortisol
Dogs with iatrogenic hyperadrenocorticism: Flat Line (no change)
If at 4 hours on the LDDStest cortisol suppressed by greater than 50% baseline value
PPDH
What are clinical signs for hyperadrenocorticism in a Ferret?
Alopecia
Lethargy
Muscle Atrophy
Vulvar enlargment in females
What are the clinical pathology findings of Ferrets with hyperadrenocorticism?
Anemia
Pancytopenia
Estrogen toxicosis
What is thepathogenesis of Primary Hypoadrenocorticism?
Immune mediated destruction of adrenal cortices
What is the pathogenesis of Secondary Hypoadrenocorticism?
Destructive lesion in the hypothalamus or pituitary resulting in less corticotropin-releasing hormone or less ACTH
What are the clinical pathology findings of Hypoadrenocorticism?
Lack of Aldosterone Hyponatremia Hypotension Pre-renal azotemia Addisonian Crisis Lack of Stress Leukogram Nonregenerative Anemia Increased BUN Hypoglycemia
What are the clinical signs of Hypoadrenocorticism?
Anorexia Lethargy Thin Vomiting Weakness Dehydration Bradycardia Melena Hypothermia Painful abdomen
What are the two ways to diagnose Hypoadrenocorticism?
Electrolytes
ACTH Stimulation test
What is the test of choice for diagnosis of Hypoadrenocorticism?
ACTH Stimulation Test
