Thyroid can affect dog's personality and coat quality

June 09, 2004

A reader called for information about the thyroid. It seems that her dog obedience trainer told her that her dog's temperament could be caused by the thyroid. Then the next time she took her pet to the groomer, she was told that the poor coat could be caused by the thyroid.

The caller couldn't understand how one organ could affect both the personality and the coat quality. She felt that the poor thyroid was being used like we often use the term "flu" for a cold, bronchitis or pneumonia. Her question was, "How does the thyroid function and what are the consequences if it doesn't function?"

I had to do some digging since it has been a long time since I even thought about the thyroid. To answer the first question, yes, the thyroid can affect both the personality and coat quality.

In regards to how the thyroid functions and the consequences if it doesn't function, let's start with a definition. The thyroid gland is an important organ that regulates metabolism. It is located in the front of the neck just below the voicebox (larynx).


According to the Endocrine Web site, the function of the thyroid gland is to take iodine, found in many foods, and convert it into thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid cells are the only cells in the body that can absorb iodine. T3 and T4 are then released into the blood stream and are transported throughout the body where they control metabolism, which is the conversion of oxygen and calories to energy. Every cell in the body depends upon thyroid hormones for regulation of their metabolism.

The thyroid gland is under the control of the pituitary gland, a small gland the size of a peanut at the base of the brain. When T3 or T4 drop too low, the pituitary gland sends a signal to the thyroid gland to increase production. The pituitary gland is regulated by another gland known as the hypothalamus, which is part of the brain. The hypothalamus signals the pituitary to signal the thyroid for the increase of T3 and T4.

Early symptoms of hypothyroidism are: weakness, fatigue, cold intolerance, constipation, weight grain, depression, joint or muscle pain, thin brittle nails, and thin brittle hair. Later symptoms include: lethargy, drooping of the eyelids, mental dullness, hoarseness and irregular heat cycles.

Tests may reveal a slow heart rate, low blood pressure and low temperature.

Now you will understand why two different people mentioned the thyroid for two totally different reasons.

Hypothyroidism is not as bad as it sounds since it is possible to provide the necessary hormones in pill form. It may take two or more visits to the veterinarian to regulate the number of pills needed each day, but fortunately, the pills themselves are not that expensive, because the dog will probably need them the rest of its life. One of my dogs takes two thyroid pills each day.


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