Does Your Dog’s Thyroid Work Properly?

Does Your Dog’s Thyroid Work Properly?

How much do you know about thyroid function in dogs? Over the last few years a lot of attention has been paid to the connection between the thyroid and behaviour of our best friends. It makes interesting reading.

Jean Dodds a popular veterinary scientist has carried out a study on how the thyroid affects the behaviour of our dogs on a daily basis, inclusive of the effects of faulty thyroid function. We wanted to make you aware of this study and the thyroid in general, because thyroid problems can often be misdiagnosed or not recognised at all.

The thyroid is responsible for producing two types of hormone that regulate metabolism in dogs. The collective is referred to as Thyroid hormone. When the thyroid does not work properly it can cause one of the two following conditions;


This condition is the result of the thyroid producing less hormone than it should, or where the hormone is not properly stimulated thus rendered ineffective. This is a particularly serious condition in young animals as the lack of thyroid hormone as it can slow down growth and development.

Hypothyroidism means that the body receives too little good quality thyroid hormone. Reduced hormone causes all body systems and organs to slow down and the following symptoms begin.

  • Lethargy
  • Physical and mental weakness and inactivity.
  • Weight gain even when food is reduced.
  • Poor coat due to hair loss, shedding and slowing of coat growth. Skin
  • Excessive scaling
  • Recurring skin problems


This disorder of the thyroid means that the gland is producing far more hormone than it should. With hyperthyroidism the metabolism rate increases and the body is literally sped up as are all of the organs within it, by the increased amount of hormone the thyroid is producing. Hunger and weight loss

  • Lack of condition
  • A lump on the neck/enlarged thyroid
  • Hyperactive busy behaviour.
  • Vomiting and/or loose bowel movements
  • Excessive thirst and urination
  • Breathing problems such as seeming out of breath or breathing too quickly.
  • Heart murmur; rapid heart rate; particularly an abnormal heart beat known as a “gallop rhythm”

The study was carried out to try and work out whether sudden aggression in dogs could be related to thyroid dysfunction and also to work out whether the lesser signs of thyroid problems were a lead up to an aggressive response. Dodds states that;

“The clinical signs in these animals, before they show the sudden onset of behavioural aggression, can include minor problems such as inattentiveness, fearfulness, seasonal allergies, skin and coat disorders, and intense itching. These may be early subtle signs of thyroid dysfunction, with no other typical signs of thyroid disease being manifested”. (W. Jean Dodds, DVM)

It makes sense that, in a dog’s body, when a specific hormone regardless of its function is unregulated that the dog’s reaction to things will be equally erratic. The worrying thing is that skin problems and other external symptoms can be treated yet thyroid dysfunction easily overlooked until the behaviour becomes severe.

So if your dog shows any of the symptoms discussed here it may be worth getting a blood test for him, one that specifically tests thyroid function.