Unusual Manifestations of Feline Hyperthyroidism and Feline Thyroid Storm

Thyrotoxicosis is a term used to describe any condition in which there is an excessive amount of circulating thyroid hormone whether from excess production and secretion from an overactive thyroid gland, leakage from a damaged thyroid gland, or from an exogenous source. In most veterinary patients, thyrotoxicosis occurs from thyroid gland hyperfunction. Feline hyperthyroidism is a common endocrinopathy in middle-older aged cats and most often the cause of thyrotoxicosis seen by veterinarians. The clinical presentation of thyrotoxicosis in veterinary patients can vary tremendously from asymptomatic biochemical changes to lifethreatening, multisystemic disease. In humans, one form of acute thyrotoxicosis is called thyroid storm and is a cause of significant mortality in human emergency rooms. Thyroid storm is uncommon, and the signs can go unrecognized, thus contributing to the high degree of mortality associated with this disease. In humans, thyroid storm can occur at any age. It can be present in euthyroid patients as well as treated and partially-treated hyperthyroid patients.