What is hypothyroidism

Hypothyroidism is a common endocrine disorder often seen in middle to older aged dogs, caused by a decrease in the thyroid hormones produced by the thyroid gland. An underactive thyroid can have consequences on the body’s metabolism.

A brief description

The thyroid gland, located in the lower neck, is divided into two parts called lobes which are positioned either side of the windpipe (trachea). It is here where thyroid hormones important for metabolism, mainly thyroxine (T4) and to a lesser extent triiodothyronine (T3), are produced.

The thyroid hormones play a central role in your dog’s carbohydrate, fat and protein metabolism, and they also affect the heat balance. Hypothyroid dogs may become apathetic, weak, sleep more frequently or for longer periods of time, inclined to suffer chills, or gain weight without changes to its diet.

What causes hypothyroidism?

The most common cause is an immune system disease causing the body’s immune system to overreact. The thyroid gland becomes inflamed as a result of the action of antibodies directed against the body’s own tissues. This stage is referred to as an autoimmune-mediated lymphocytic thyroiditis.

Other causes of hypothyroidism, such as tumours of the thyroid gland, radiation and congenital thyroid disorders are very rare.

Occasionally, a tumour of the pituitary gland can also cause hypothyroidism. This is referred to as secondary hypothyroidism.