The thyroid gland is a small gland that works in conjunction with the pituitary gland that controls hormones called thyroxine and triiodothyronine, commonly known as T4 and T3 respectively. Just like with people, dogs can have issues with their thyroid gland. Typically, when a dog has issues with their thyroid gland, it is hypothyroidism. Basically, this is just a fancy medical term that means the body produces less than the normal amount of thyroid hormones.
There are two common reasons that a dog develops hypothyroidism, lymphocytic thyroiditis and idiopathic atrophy. Lymphocytic thyroiditis is a genetic autoimmune disease. Idiopathic atrophy basically means the cause is unknown. Most dogs start showing clinical signs of hypothyroidism before the age of 6 years old – with a majority between the ages of 1-3 years old. Like most autoimmune endocrine diseases, hypothyroidism is more common in females than males.
As previously stated, some hypothyroidism is due to genetics and there are certain breeds that are predisposed. Golden retrievers, doberman pinschers, dachshunds, Shetland sheepdogs, Irish setters, airedales and cocker spaniels make up that list of breeds with a higher risk of thyroid issues.
Symptoms of hypothyroidism may include:
- Loss of hair – often around the flank (abdomen), hind quarters and tail
- Dry, scaly or thickened skin
- Dull, brittle hair
- Hair coat thinning or patches of alopecia (hair loss)
- Bleaching of the hair coat
- Development of oily skin
- Lethargy (less active)
- Being overweight or significant weight gain, even though they have a controlled diet
- Being uninterested in favorite activities
- Intolerant of cold
- Slower heart rates
- Breeding females birth puppies with lower birth weights and decreased vitality.
After our veterinarian does a physical exam and observe signs of hypothyroidism, they will recommend blood panel to review the level of dog’s thyroid hormones.
The following factors can falsely alter the thyroid hormone levels:
- The time of day the blood was drawn. Dogs T4 levels fluctuate every 20-30 minutes.
- The age of the dog.
- Dogs on NSAIDs like carprofen (Rimadyl) will have lower a T4 level.
- The breed of the dog. Not only are there certain breeds that are more prone to hypothyroidism but sight hounds like the greyhound actually have a normal lower T4 level than other dog groups.
If your dog has a lower T4 but falls into one of the above categories, additional testing to include T3 test may be recommended. In some cases a full thyroid panel is necessary to find a precise answer as to how your dog’s thyroid gland is working.
If your dog is not producing enough thyroid hormone, they will have to be supplemented with a canine thyroid medication. Usually this medication is given orally twice a day. You can start to see improvement with your dog’s overall health in 2-4 weeks but it may take up to 6 months to see any changes in your pet’s coat. After your dog has been on thyroid medication for a month or two, a repeat thyroid screening is necessary to evaluate how the medication is working. Sometimes, the dosage will need to be adjusted to keep the dog’s thyroid hormone within normal range. This process may take several blood tests to find the optimal dose for your individual pet. Once controlled, annual physical exams and blood screening will be necessary. With proper thyroid supplementation and blood screening, your dog can live a happy, long life.