Can a Dog Have Both Hyperthyroid and Hypothyroid Signs?

Dogs have one thyroid gland with two lobes. Some dogs also have small patches of extra (ectopic) thyroid tissue elsewhere in the neck or chest. An overactive thyroid is rare in dogs and usually comes from a thyroid tumor, too much thyroid medication, or raw diets or treats containing thyroid tissue. Weight loss with a big appetite is more often caused by diabetes, intestinal problems or other diseases.

A slow heart rate can have several causes, and your vet may suggest an ECG. Blood and urine tests, including a thyroid panel, are a good start.

See hypothyroidism in dogs.

This is general information, not a diagnosis. Please follow your own vet's advice.