Endocrine 3 Flashcards
What are some clinical signs of hypothyroidism?
-Reduced basal metabolic rate (weight gain)
-bilaterally symmetrical alopecia
-hyperkeratosis
-hyperpigmentation
-myxedema
-hypercholesterolemia leading to atherosclerosis
What are two examples of congenital hypothyroid disorders?
Goiters, CHDS in foals
What is a goiter?
A non-specific term used to describe a non-neoplastic, non-inflammatory enlargement of the thyroid glands
What are four causes of goiters?
Iodine deficient diets, goitrogenic compounds, excess dietary iodine, genetic enzyme defects (dyshormonogenetic goiter)
What is the pathogenesis of a goiter?
Inadequate thyroid hormone synthesis → decreased blood levels of T3 and T4 → increased TRH → increased TSH → hypertrophy/hyperplasia of follicular cells
What is congenital hypothyroidism-dysmaturity syndrome (CHDS) in foals?
A condition in foals causing perinatal death and MSK malformations (have a prolonged gestation but appear to be born premature)
How can you diagnose CHDS in foals?
Grossly the thyroid may look normal, but microscopic lesions are present. If you are suspicious based on the clinical signs, make sure to ALWAYS TAKE THYROID FOR HISTOLOGY!
What are the two most common endocrine diseases of cats?
Hyperthyroidism, diabetes mellitus
What mechanism of endocrine disease is hyperthyroidism?
Primary hyperfunction (#2)
Why is hyperthyroidism less common in dogs?
Dogs are very good at excreting excess iodine versus cats are bad at conjugating excess thyroid hormone and iodine
What are the clinical signs of hyperthyroidism?
Increased basal metabolic rate (cachexia), hyperexcitable and heat intolerant, tachycardia and dysrhythmias, PUPD, concentric hypertrophy of the heart (do not get this confused with HCM - heart lesions due to hyperthyroidism are reversible)
What are three proliferative thyroid lesions that cause hyperthyroidism?
Thyroid follicular adenoma, thyroid follicular carcinoma, multifocal nodular hyperplasia
When dogs develop a thyroid lesion, is it more likely to be benign or malignant? What is this neoplasia called?
Malignant (thyroid follicular carcinoma)
When cats develop a thyroid lesion, is it more likely to be benign or malignant? What is this neoplasia called?
Benign (thyroid follicular adenoma)
What does multifocal nodular hyperplasia look like grossly?
Multiple tan to brown non-encapsulated nodules
Can’t differentiate from follicular cell adenoma grossly
Multifocal nodular hyperplasia is most common in which species?
Cats (functional/active in cats versus inactive in other species)
Thyroid follicular cell adenomas are most common in which species?
Cats
What do thyroid follicular cell adenomas look like grossly?
Single, white to tan, well-defined, and encapsulated
Can’t differentiate from multifocal nodular hyperplasia grossly
Thyroid follicular cell carcinomas are most common in which species?
Dogs (invasive and early metastasis to the lungs)
What do thyroid C-cells secrete? What is the function of this hormone?
Calcitonin. To decrease blood calcium levels (stimulated by high blood calcium levels)
What are thyroid C-cell tumors?
Neoplasias derived from C cells (parafollicular cells) of the thyroid gland
What is the cause of thyroid C-cell tumors?
Cause is unknown but likely related to high calcium diets
Which species do thyroid C-cell tumors occur most commonly in?
Old bulls (they get fed the same thing as dairy cows sometimes but the difference is that the bulls don’t have the reservoir for calcium because they aren’t lactating)
True or False: Thyroid C-cell tumors can be both benign and malignant
True