Endocrine3- Thyroid Patho
Card Set Information
Endocrine3- Thyroid Patho
Aberrant ectopic thyroid parenchyma is usually __________, and usually occurs in _________ and sometimes __________.
microscopic; dogs; cats
Ectopic thyroid tissue behaves like...
normal thyroid tissue- iodine ion uptake, colloid formation, thyroid hormone secretion, absence of C cells
What is the significant of ectopic thyroid tissue? (3)
total surgical thyroidectomy is difficult, hyperplasia in iodine deficiency, neoplasia from base of tongue to base of heart
What is persistence of thyroid remnants at base of tongue called?
What is the significance of foramen caecum? (2)
cysts, neoplasms at base of tongue
What causes trophic atrophy of the thyroid? (2)
subnormal TSH production due to pituitary neoplasm or space-occupying mass compressing pituitary
What causes pressure atrophy of the thyroid gland? (3)
bilateral lesions adjacent to thyroid- cervical cyst, abscess, neoplasm
What are 2 causes of thyroid atrophy?
trophic atrophy, pressure atrophy
Common causes of hypothyroidism. (2)
lymphocytic thyroiditis (immune-mediated), follicular atrophy (idiopathic)
Idiopathic thyroid atrophy is aka ___________; it is a(n) _____________ lesion and results in _______________.
"follicular collapse"; non-inflammatory degenerative; adipose connective tissue replacement of thyroid tissue
Idiopathic thyroid atrophy only occurs in _________.
Histologically, with idiopathic thyroid atrophy, you see... (2)
C cells and adipocytes.
TSH is _________ in dogs with idiopathic thyroid atrophy.
very high (trying to stimulate thyroid that is non-functional)
What species can be affected by lymphocytic thyroiditis? (4)
dogs, chickens, rats, primates
What are thyroid antigens that are attacked with thyroiditis? (4)
thyroglobulin, thyroperoxidase, TSH receptor protein, secondary antigens (colloid, nuclear, cytoskeletal, proteins, tubulin)
Describe the immune response with thyroiditis.
immune-mediated: humoral autoantibody production, sensitized T cells, antibody-independent cytotoxicity
Thyroid neoplasms can affect... (2)
follicular cells or C cells.
Describe a thyroid adenoma clinically. (4)
palpable mass in anterior cervical area, freely moveable, compression of adjacent structures, hypersecretion of thyroid hormones
In what species are thyroid adenomas malignant? (1) Benign? (2)
malignant- dog; benign- cat and horse
What are the first and second most common neoplasms in dogs?
#2- thyroid adenocarcinoma
What directly correlates with the incidence of malignancy of thyroid tumors in dogs?
the size of the neoplasm (larger--> more likely to met)
What is frequently the earliest site of metastasis of a thyroid tumor in a dog? What is a later site of metastasis?
late- bone (hypercalcemia)
Why are dogs with thyroid tumors not usually hyperthyroid?
dogs are extremely thyroid resistant- their liver can metabolize/remove thyroid hormone very effectively
What is the most common morphologic type of thyroid carcinoma?
follicular-compact cellular carcinoma
- tumor is a solid mass made up of follicular cells
What are the types of undifferentiated thyroid carcinoma? (3)
small cell, giant cell (spindle cell), malignant mixed (causing osteosarcoma or chondrosarcoma)
Undifferentiated thyroid carcinomas have a ________ prognosis than follicular and C cell carcinomas.
What is the only known carcinogen of the thyroid gland?
Who is most at risk for thyroid cancer after radiation exposure?
young children and animals (young have much more active thyroid glands)
How do you prevent thyroid cancer in the wake of ionizing radiation exposure?
sodium iodide and potassium iodide, saturating the system and preventing radioactive iodide from being taken up by the thyroid
What are possible causes of feline hyperthyroidism?
iodine in diet, iodine-containing food dyes, environmental goitrogens, environment carcinogens
Feline hyperthyroidism occurs due to... (3)
benign functional thyroid adenoma, multinodular follicular hyperplasia, or follicular adenocarcinoma (very rare).
Feline hyperthyroidism is usually a _________ disease.
What is a common location for ectopic primary thyroid neoplasms?
base of the heart (other differentials- malignant lymphoma, aortic body tumor)
What is goiter?
hypertrophy and hyperplasia of follicular cells; non-neoplastic, non-inflammatory
Goiter occurs in people due to __________.
With iodine deficiency TSH _________ due to...
increases; lack of thyroid hormone (trying to stimulate thyroid gland).
People with goiter are _________ but __________ because of compensation.
iodine deficient; euthyroid
Cows can end up with goiter if...
farmer buys the wrong salt blocks (non-iodinated).
Lack of iodine has the greatest effect on...
young animals and fetuses.
Congenital form of goiter occurs in __(2)__.
goats and sheep
Describe congenital goiter.
congenital defect in thyroglobulin; dwarfs, decreased mentation, independent of iodine deficiency.