ABSTRACT
Myxedema coma is a rare but life-threatening end result of chronic, severe hypothyroidism in dogs. Affected dogs most commonly described in the veterinary literature are middle-aged Doberman pinschers, but other breeds have been reported as well. Multiple organ systems are involved, including the cardiovascular, respiratory, thermoregulatory, dermatologic, and neurologic systems. Early recognition of the syndrome with appropriate, controlled treatment improves survival in dogs with myxedema coma, although the mortality rate may reach 50%. These can be secondary to lack of stimulation of the sinoatrial cells by thyroid hormone and decreased contractility due to reduced numbers of B receptors on the myocardium. Thyroid supplementation must be begun via parenteral routes because oral bioavailability of thyroxine is low and can be slow in onset. Thyroid storm is a rare but life-threatening complication of hyperthyroidism in humans. As stated before, laboratory values generally do not differentiate between thyroid storm and severe thyrotoxicosis.
