Diagnosis + Treatment of Disease- Thyroid Gland Flashcards
(28 cards)
Where is the thyroid gland located?
2 lobes either side of the trachea, just below the larynx
With regard to dogs + cats, is the thyroid gland usually palpable?
No
Name 3 disorders of the thyroid gland
Hypothyroidism
Hyperthyroidism
Goitre
Name two methods to diagnose thyroid disease
Clinical signs
Blood tests
What blood tests can be used to detect thyroid disease?
Total T4
Free T4
Endogenous canine TSH
Thyroglobulin autoantibodies
Why can endogenous canine TSH be used to detect thyroid disease?
Comes from the pituitary gland + drives the production of TH
What results would you expect from the blood tests of an animal with HYPERthyroidism?
High serum T4 (total)
Describe two methods that could be used to treat HYPERthyroidism
- Remove thyroid tissue through surgery or radioactive iodide
- Reduce synthesis of thyroid hormone from existing tissue by restricting iodine + blocking synthesis with thioureylenes
What are the cons of thyroidectomy?
- Upfront cost
- Risk of damage to parathyroid glands
What role does the parathyroid gland play?
Very important in Ca regulation
Describe + explain how radioactive iodide can be used to treat HYPERthyroidism
- Destroys thyroid follicles
- rapidly incorporated into thyroid follicles
- half life 8 days + serum T3/ T4 start to normalise after 1-2 wks
What are the cons of using radioactive iodide to treat HYPERthyroidism?
- Treated animals must be hospitalised for 1-4wks
- Treated animals + excreta need to be handled carefully until radioactivity is gone
- VV expensive
What is the main pro of radioactive iodine compared to surgical thyroidectomy to treat HYPERthyroidism?
less risk of hypocalcaemia
Describe the adverse effects that could occur after removing thyroid tissue?
- HYPOthyroidism
- Bilateral disease- damaged PTH + hypocalcaemia (from bilateral thyroidectomy)
Name the thioureylene used in the UK
Carbimazole
Name the thioureylene used overseas
Thiamazole
Describe how the UK thioreylene works to block synthesis of iodine?
- Carbimazole metabolised to methimazole = inhibits synthesis of T3 + T4
- GI absorption after oral administration, widely distributed
- Metabolised by hepatocyte P450 enzymes followed by conjugation w/ glucuronide (classic phase 1 + 2 of liver metabolism)
How long would you predict before free T3 + T4 decline after treating with carbimazole?
3 weeks
What adverse effect may occur after treatment w/ carbimazole?
HYPOthyroidism
What is the most common endocrine disorder in dogs?
HYPOthyroidism
How would you test for HYPOthyroidism?
Total T4
Free T4
Endogenous TSH
Thyroglobulin autoantibodies
Explain why Total T4 is not a reliable test for HYPOthyroidism
Breed, age + drugs can affect T4 values + sick euthyroid syndrome- if Total T4 is low, dog may not actually be hypothyroid
What is meany by ‘sick euthyroid syndrome’`?
Low T4 is shown with ANY sick dog- not necessarily hypothyroidism
What is the most common cause of HYPOthyroidism in dogs?
Thyroglobulin autoantibodies
