What Are Normal Thyroid Levels in Dogs?

The thyroid levels in dogs indicate the function of the thyroid glands. If you suspect that your pet may have hypothyroidism or hyperthyroidism, you may want to get some tests done that will indicate the levels of the thyroid hormones in the body. However, when getting the results you may want to know how to interpret the results. The levels of hormones will depend on the dog’s age, breed and may also depend on other factors.

The Tests for Thyroid Levels

The tests that will indicate the thyroid levels will measure the thyroid hormones. The thyroid hormones are:

  • T4 or thyroxine
  • T3 or triiodothyronine

These hormones regulate the dog’s metabolism and perform other functions as well. The T3 and T4 hormones are produced by the thyroid glands, which are found at the base of the neck.

The level of the thyroid stimulating hormone (TSH) will also have to be measured, as even if this is not produced by the thyroid glands, it is in charge with controlling the T4 and the T3 hormone production. If the levels of TSH are not normal, the T3 and T4 levels are most likely affected as well. The TSH hormones are produced by the pituitary gland.

Normal Thyroid Levels

The normal thyroid levels will depend on several factors such as the age, weight and breed of the dog. The time of the day may also count when it comes to the levels of thyroid hormones. The level of thyroid hormones may also be increased after meals.

Consequently, there are no averages that can be used as guidance when getting the test results.

A vet alone can interpret the results and consider all the possible factors that may influence the levels of the thyroid hormones.

Thyroid Level Determination

There are numerous tests that may be used to determine the levels of thyroid hormones in dogs. The assay tests will measure the T4 and T3 levels and should be performed if the dog displays symptoms of thyroid dysfunction. The most commonly used assay tests include the radioimmunoassay (RIA) and the enzyme-linked immunosorbent assay (ELISA) test.

Possible Causes of Abnormal Thyroid Levels

The abnormal thyroid levels may be determined by a wide range of medical conditions. If the thyroid levels are below the normal range established by the vet, the dog is affected by hypothyroidism.

A dog with higher thyroid levels will be diagnosed with hyperthyroidism.

The abnormal thyroid levels may be caused by:

  • An abnormal growth affecting the thyroid glands
  • A tumor affecting the pituitary gland, which will affect the production of TSH and disturb the normal production of T4 and T3 hormones
  • Autoimmune diseases
  • Medication for hyperthyroidism, which can result in a production of thyroid hormones that is lower than normal
  • A birth defect that affects the thyroid glands or the pituitary gland
  • Treatment with radiotherapy, which can reduce the production of thyroid hormones.