Hyperthyroidism (thyrotoxicosis) is uncommon in dogs. When it occurs, the cause is quite different from the cat. A dog with a high T4 either has a functional thyroid carcinoma or is getting thyroid hormone from outside: from raw meat, gullets or treats that contain thyroid tissue, or from too much levothyroxine. Most dogs with thyroid tumors are not hyperthyroid at all, so this guide covers both the hormone problem and the tumor.
Key facts
Hyperthyroidism at a glance- Species / system: Dog; thyroid gland (endocrine) and head and neck oncology.
- Causes of thyrotoxicosis: functional thyroid carcinoma; exogenous (dietary) thyroid hormone from raw meat containing thyroid tissue, gullets, head meat or contaminated commercial food and treats; levothyroxine overdose.
- Thyroid tumors: about 90% of those found clinically are carcinomas. Only about 10–20% make excess hormone; most dogs are euthyroid.
- Classic presentations: an older Golden Retriever, Beagle, Siberian Husky or Boxer with a firm mass in the ventral neck; or a younger raw-fed dog with a high T4, weight loss and restlessness and no mass.
- Key decision: is the tumor mobile (surgery) or fixed and invasive (radiation or radioiodine)?
- Not zoonotic or reportable. Contaminated pet foods are a regulatory (FDA) issue.
What's inside
12 sections in the full guide- Key facts
- How the NAVLE tests this
- Cause and pathophysiology
- Clinical signs
- Diagnosis
- Differential diagnoses
- Treatment and management
- Prevention
- Prognosis
- Quick review
- Test yourself
- References
The full guide also has 5 tables, 2 figures, 3 self-test questions and 22 references, available to NAVLE members.
Read the full study guide
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