The thyroid gland helps to regulate the body’s metabolism by producing hormones. Hypothyroidism is an underactive thyroid gland. In dogs, hypothyroidism is commonly diagnosed between the ages of four to ten years. Hypothyroidism occurs more commonly in large breed dogs.
The thyroid gland is a paired lobed gland located in the throat area on either side of the trachea. Hypothyroidism in dogs is thought to be an immune-mediated disease called lymphocytic thyroiditis. The immune system attacks the cells in the thyroid gland causing inflammation and atrophy of the gland. Over time the thyroid gland’s activity decreases with a subsequent decreased production in the thyroxine hormone. It is unclear why this condition occurs; however, it is a heritable trait meaning that genetics likely plays a role in this condition.
There are several types of blood tests used to diagnose and monitor hypothyroidism including Total T4, free T4, and TSH. Thyroxine (T4) is the primary hormone produced by the thyroid gland. T4 circulates in the blood in two forms; one form of the hormone is bound, or attached to proteins in the blood, while the other form circulates freely within the blood stream. TSH (Thyroid Stimulating Hormone) is produced by the pituitary gland to regulate the thyroid gland’s activity.
Hypothyroidism is treatable but not curable. The recommended treatment is administration of an oral synthetic thyroid hormone replacement called levothyroxine. Thyro-Tabs, an FDA approved formulation of levothyroxine comes in a pill is available. Cost effective generic medications are also available. The medication is normally given once or twice a day. The dose and frequency administered will be determined by your veterinarian. Levothyroxine is generally well tolerated with minimal side effects. Treatment of hypothyroidism is life long, meaning this drug must be given for the rest of the dog’s life.
Canine patients with hypothyroidism will need regular progress exams and diagnostic tests performed by a veterinarian. Once the dog is tested and put on medication, they will have to be rechecked one month later to verify the levothyroxine dose is effective. Your pet will have to be on thyroid medication for the rest of its life. Routine thyroid testing should be done on a yearly basis or if symptoms change.
With treatment, the prognosis for hypothyroid dogs is good. Hypothyroidism cannot be cured, but most symptoms will improve with consistent administration of medication. Pets that consistently receive their medication and are monitored regularly by their veterinary have a normal life expectancy. Treatment and control of the hypothyroid pet generally provides very rewarding results for both the patient and the owner.