Hyperthyroidism and hypothyroidism are among the most common endocrinopathies affecting feline and canine patients, respectively, in middle age and geriatric years. This course will provide veterinary professionals the information they need to identify the common clinical signs as well as the unusual manifestations of thyroid disease. In addition, we will cover the importance of routinely screening patients with suspected or potential thyroid disease, since the onset of thyroid disease is often insidious in senior pets–occurring over months to years. We will review the available diagnostic tests for thyroid disease and the indications for each. Lastly, current treatment options and therapeutic monitoring protocols will be reviewed.