Thyroid and Parathyroid Gland Flashcards
What hormone does the thyroid gland secrete? Are the hormones secreted at equal concentrations?
T3 and T4
80-90% secreted hormone is T4
Most T3 is from T4 conversion peripherally
What species requires a more sensitive assay for T3 and T4?
Dog - they have lower levels
Are thyroid hormones protein bound? Are there free hormones?
Yes, ~99% are protein bound. Free hormones are the active component
What form of thyroid hormone is most active?
fT3 (3-5 time > fT4)
Euthyroid animal
The state of having normal thyroid gland function
What can decrease total hormone measurements in a euthyroid animal?
Hypoproteinemia
How do you diagnose thyroid conditions?
Must measure thyroid hormones. Use clinical info to suggest there may be a problem.
What species is hyperthyroid common? What is the most common pathology of the thyroid for this species?
cats
Hyperplasia, adenoma most common
What is the typical hyperthyroid signalment and history in cats?
thin
older
hyperactive
polyphagia
What erythron abnormality is common in hyperthyroid animals? Why?
Polycythemia
Increase basal metabolic rate and oxidative metabolism–> increase tissue demand for oxygen –> increase RBC production to meet this demand
What is often diagnostic alone for hyperthyroidism?
Increased resting T4, free T4
What thyroid conditions is most commonly seen in dogs? What is the pathology of the lesion?
Hypothyroidism
glandular atrophy or lymphocytic thyroiditis
What are three dog breeds predisposed to hypothyroidism?
Doberman
Dachshund
Cocker
How does hypothyroidism cause non-pitting edema?
Low metabolic rate –> slow turnover of CT –> build up of CT in tissues –> osmotic potential
What will the erythron look like with hypothyroidism?
Mild, non-regenerative anemia
decrease oxidative metabolism
T/F
Hypothyroid dogs present similarly to cushing’s dogs
True
Use hematology to distinguish!
What clin chem value may be strongly suggestive of hypothyroidism?
> 500 mg/dl cholesterol
What are some other R/O for hypercholesterolemia?
Pancreatitis
Cholestasis
DM
Renal failure/ nephrotic syndrome
What is “Sick Euthyroid Syndrome”?
When a disease will cause low levels of thyroid hormone.
Common in ICU patients - not necessary to test them for hypothyroid
What diseases may cause sick euthyroid syndrome?
Cushing's DM Addison's Chronic RF Liver disease Several types of dermatoses (pyoderma)
Why does renal failure cause hypercholesterolemia?
Loss of albumin –> decrease oncotic pressure –> liver produces more cholesterol to compensate
What diseases are hypercholesterolemia seen with?
Pancreatitis Renal failure (most consistent with renal loss) Hepatobiliary disease Cushings Hypothyroidism DM
Should you supplement sick euthyroid patients?
Not recommended
Thyroid hormones will return to normal after primary condition is resolved
What drugs may cause sick euthyroid syndrome?
Anesthetics (surgery)
NSAIDS
Furosemide
Glucocorticoids
What does PTH do? What does calcitonin do?
PTH - ↑ Ca and ↓ P
Calcitonin - ↓ Ca and ↓ P
What is primary hyperparathyroidism?
Usually due to parathyroid neoplasm
Increase PTH from parathyroid gland –> increases Ca and decreases P
How can you use urine Ca levels to suggest excess serum PTH?
Low calcium in urine
High calcium in blood
What may make the Phosphorus levels appear normal or increased in a primary hyperparathyroid case?
Renal azotemia
What is pseudohyperparathyroidism?
aka - Humoral hypercalcemia of malignancy (HHM) #1 is lymphoma #2 is anal sac tumor
What is the classic pattern for hypervitaminosis D?
Increase Ca and normal to increase P (without azotemia)
what are 3 differentials for hypervitaminosis D?
- Oversupplementation
- Cholecalciferol based rodentocides
- Plants
