Dog Thyroid

Thyroid hormones act on many different cellular processes. Some of their actions occur within minutes to hours, while others take several hours or longer. Thyroid hormones in normal quantities work along with other hormones, such as growth hormone and insulin, to build tissues. However, when they are secreted in excess, they can contribute to breakdown of proteins and tissues.

hypothyroidism, decreased levels of thyroid hormones result in a slower metabolic rate. More than 95% of cases of hypothyroidism in dogs are caused by destruction of the thyroid gland itself. Another cause is a tumor of the pituitary gland, which usually causes deficiencies of other pituitary hormones as well. Rarely, dogs can be born with a thyroid gland that does not develop or function normally. Puppies born with a pituitary disorder, such as pituitary dwarfism, can also have hypothyroidism.

Hyperthyroidism is caused by excess of the thyroid hormones, T3 and T4. Signs include weight loss, increased appetite, excitability, increase in thirst and urination, vomiting, diarrhea, and increased heart rate, all of which reflect an increased metabolic rate. Hyperthyroidism is much more common in cats than in dogs. When it does occur in dogs, the most likely cause is malignant cancer of the thyroid gland (thyroid carcinoma).

---