Many factors can influence your hyperthyroid cat’s long-term prognosis. The key one is whether their thyroid is appropriately controlled with treatment, and perhaps to a slightly lesser degree, what treatment they receive. Other concurrent things that can affect their prognosis include kidney disease, cancer, or heart conditions. In a well-controlled cat, it is usually these secondary diseases that affect survival rates the most. Your cat must attend regular examinations and screening tests, as this will ensure their hyperthyroidism is well managed. Some hyperthyroid cats can live for a few more years following diagnosis and following your vet’s advice will help with this.