Hyperthyroidism in cats is due to an overactive thyroid gland that can develop a benign tumor. Look for weight loss in cats that have hyperthyroidism withhelp from a staff veterinarian in this free video on cat health and pet care. Expert: Dr. James Talbott Bio: Dr. James R. Talbott is a staff veterinarian at Belle Forest Animal Hospital and Kennel in Nashville, Tenn. Filmmaker: Dimitri LaBarge