Physiology of hyperthyroidism Flashcards
1
Q
FACTSHEET
A
Hyperthyroidism=
- Excessive production of T4
- Adenomatous hyperplasia of thyroid glands
- Mainly bilateral in cats
- Hyperthyroidism results in multi organ dysfunction
2
Q
Is feline hyperthyroidism usually unilateral or bilateral?
A
Bilateral
3
Q
Like risk factors for developing hyperthyroidism
A
- Canned products = may be high in iodine or other goitrogens
- Breeds (rare in Siamese)
- Age (10+)
4
Q
List some of the clinical signs associated with hyperthyroidism
A
- Weight loss
- Polyphagia
- PUPD
- Tachycardia
- Diarrhoea
- Vomiting
- Haircoat changes
- Goitre
- Hypersensitve to heat
5
Q
Why can hyperthyroidism cause vomiting?
A
- Activation of the emetic centre
- Due to overeating
6
Q
What behavioural changes are associated with hyperthyroidism?
A
- Hyperactivity
- Vocalisation
- Obsessive grooming
7
Q
Why does hyperthyroidism cause hypertrophic cardiomyopathy?
A
-Thyroid hormones have a direct effect on the myocytes
Indirect compensatory changes due to altered peripheral perfusion
8
Q
What tests can be used to diagnose hyperthyroidism?
A
- Baseline= Total T4 (normal a single test is enough to diagnose but may need repeating)
- T3 suppression test
- Thyroid scintigraphy
9
Q
What are the limitations of the total T4 test?
A
- Daily fluctuations
- May be normal in early stages of the disease
10
Q
Describe the T3 suppression test
A
- In normal cats an injection of exogenous T3 should cause a decrease in TSH and T4
- In hyperthyroid cats you have a very minimal decrease in T4
11
Q
Describe thyroid scintigraphy
A
- Use a radioactive marker to ID functional thyroid tissue
- Using IV injection of technetium or iodine
- Use a gamma camera to count
12
Q
Describe hyperthyroidism in dogs
A
- RARE-Only small amount of thyroid carcinomas are functional
- Highly metastatic
- Occurs in older dogs and particularly golden retrievers, boxers, beagles
