Dog Hyperthyroidism from Thyroid Adenoma Diagnosis

While rare in dogs compared to cats, hyperthyroidism does occur and usually signals functional thyroid neoplasia requiring evaluation.

Key Facts

Hyperthyroidism is rare in dogs but when present, is usually caused by functional thyroid carcinoma rather than the benign adenoma common in cats
Signs include weight loss, increased appetite, restlessness, and possible neck mass
Total T4 and TSH measurement establish the diagnosis - high T4 with low TSH confirms hyperthyroidism
Thyroid scintigraphy localizes the functional tumor and identifies ectopic thyroid tissue
Complete surgical excision is the preferred treatment when the tumor is non-invasive and non-metastatic
Radioactive iodine therapy can treat functional thyroid tumors in dogs but requires specialized centers
Dogs with concurrent non-functional tumor tissue may have competing surgical and medical treatment needs

Welfare Considerations

Hyperthyroid dogs experience persistent metabolic hyperactivity that causes weight loss, cardiovascular stress, and behavioral changes including restlessness and irritability. Untreated hyperthyroidism eventually leads to cardiac complications. Unlike in cats where medical management is often appropriate, dog hyperthyroidism usually reflects a tumor that warrants surgical assessment rather than long-term medical control.

What You Can Do

Seek prompt evaluation for any dog with unexplained weight loss despite good appetite and a visible or palpable neck mass
Request thyroid hormone testing (T4 and TSH) as part of the initial diagnostic workup
Ask about thyroid scintigraphy to map the tumor before surgical planning
Seek referral to a specialist experienced with thyroid tumor surgery in dogs
Monitor cardiac function throughout treatment as hyperthyroidism can cause cardiac complications