By Beth Guerra, DVM
The thyroid gland plays an important role in the body’s metabolism. It is a bi-lobed structure located in the neck that secretes thyroid hormone. The hormone is primarily responsible for regulating the oxygen consumption of most organs, but it also promotes overall skeletal and muscle growth. Disorders of the thyroid gland can produce too much or too little of this hormone, distorting the delicate balance of the body and leading to a variety of symptoms.
Hypothyroidism, or subnormal levels of thyroid hormone, is recognized in dogs and humans, but rarely in cats. It usually occurs in dogs around five to seven years of age, with common breeds including golden retrievers and Dobermans. Symptoms include mental dullness, lethargy, weight gain, and heat seeking behavior. Skin conditions can also occur, such as hair loss, crusting or greasiness of skin, or recurrent bacterial or yeast skin infections. It is usually a combination of these symptoms that cause a pet owner to seek veterinary attention.
Diagnosis of hypothyroidism is usually confirmed by running T4 and free T4 levels on suspect patients. Certain drugs, as well as non thyroid illnesses, can cause ‘falsely’ low T4 levels, so a full history and thorough physical exam is an important part of confirming a diagnosis. Treatment is simple and involves supplementing with oral T4, however, dose and frequency of this medication can vary between patients and therefore treatment should be closely monitored by a veterinarian. Good control of the disease is achieved through a combination of normal T4 levels as well as resolution of clinical symptoms and may take up to four months.