Hyperthyroidism in Dogs: Rare but Welfare-Significant

Unlike cats, hyperthyroidism is rare in dogs and usually indicates thyroid carcinoma rather than benign adenoma, making early detection and specialist assessment crucial for welfare outcomes.

Key Facts

Canine hyperthyroidism is rare, occurring in fewer than 1% of dogs with thyroid tumours
Most cases are associated with thyroid carcinoma rather than the benign adenoma common in cats
Signs include weight loss despite increased appetite, restlessness, and a palpable neck mass
Elevated T4 on routine thyroid testing may indicate hyperthyroidism warranting further investigation
Treatment options are limited compared to feline hyperthyroidism; surgery is the primary approach for resectable tumours

Welfare Considerations

Canine hyperthyroidism causes chronic weight loss, restlessness, and cardiovascular strain from elevated circulating thyroid hormone. The typically malignant nature of the underlying cause means welfare is compromised both by the hormonal effects and by tumour invasion. Delay in diagnosis allows the tumour to grow, reducing the chance of complete surgical resection and worsening the prognosis. Routine palpation of the thyroid region during annual health checks in predisposed breeds provides an opportunity for early detection when surgical success is more likely.

What You Can Do

Request thyroid gland palpation as part of annual health checks for predisposed large breed dogs
Seek specialist referral promptly if a neck mass is detected or if unexplained weight loss occurs despite good appetite
Discuss surgical options with a soft tissue surgeon specialist if thyroid carcinoma is confirmed
Monitor thyroid function in dogs treated for hypothyroidism to detect any shift to hyperthyroid values