Undestanding Canine Thyroid Test Results

The canine thyroid is a small endocrine gland responsible for regulating growth and metabolism in dogs. It secretes the hormones thyroxine and triiodothyronine. Malfunction of the thyroid gland is an inherited condition and it's advisable to not breed dogs that have the disease. Canine thyroid disease is relatively common and afflicts both genders. It predominantly affects young and middle-aged dogs. Once a dog develops the disease, he has it for life.

Hypothyroidism and Supplementation

Hypothyroidism occurs if insufficient amounts of the thyroid hormones are secreted. It's associated with immune system disorders that, among other negative effects, cause the destruction of the thyroid gland. This leads to a gradual decline in the amount of these hormones produced. If hypothyroidism is detected, a thyroid supplement needs to be administered. The dosage for prescribed medication is altered to suit full blown or borderline hypothyroidism. The behavioral problems are reversed within 4 to 8 weeks of onset of therapy. Therapy for hypothyroidism is for the duration of the afflicted dog's life.

Symptoms of Hypothyroidism Include:

  • Hair loss
  • Lethargy
  • Reproductive disorders
  • Obesity
  • Muscle or nerve weakness
  • Dry and flaky skin
  • Bacterial skin infections
  • Slow heart rate
  • High blood cholesterol
  • Intolerance to cold


Hyperthyroidism occurs if there's excessive secretion of thyroid hormones. It's often related to thyroid gland cancer. It can also occur if there is over-supplementation of thyroid hormones in pets suffering from hypothyroidism.

Symptoms of Hyperthyroidism Include:

  • Elevated heart rate
  • Loss of weight
  • Increased appetite
  • Increased activity

Thyroid Test

It's difficult to diagnose thyroid disease, as the symptoms are common to other diseases. The thyroid test is a blood test that reveals the levels of thyroid hormones present in the blood. If a dog exhibits the clinical symptoms of thyroid dysfunction, the vet will recommend this test as an initial diagnostic aid. During diagnosis, a blood sample is drawn from the dog and allowed to clot. The serum is then separated from the clotted blood and the levels of the thyroid hormones are analyzed.

Six Panel Thyroid Test

The six panel thyroid test is the test of choice as it measures total thyroid function. It includes Total T4, Total T3, Free T4, Free T3, T4 antibodies and T3 antibodies. The normal or standard range varies according to the dog's age and breed. The 50 percent mark of the normal range has to be determined for each panel. To obtain this 50 percent mark, the average of the end values of the range have to be determined. A dog will require thyroid hormone supplements if he falls below the 50 percent mark of these normal ranges.

Radioactive Iodine Uptake

This test determines the turnover of iodine in the thyroid gland. The disadvantages are that it's an expensive procedure, the dog has to be sedated and there's a risk of radiation exposure.

Apart from the routine tests for thyroid disease, other tests may be performed to rule out underlying health concerns. These tests include radioimmunoassay, chemiluminescence, fluorescence polarization and enzyme-linked immunosorbent assay. However, it's important to confirm that the assay is suitable to your specific canine.