Hyperthyroidism is the overproduction of the thyroid hormones T3 and T4 from the thyroid glands. It is usually caused by a non-cancerous tumor of the gland, the cause of these tumors are not known but environmental and dietary factors may play a role.
Thyroid hormones influence many of the bodies organs so the effects of overproduction are felt throughout the body.
Initially the signs are subtle but progress over time. Affected cats: