Low thyroid function in dogs is easy to diagnose and treat, but the condition often goes undetected.
Causes
Hypothyroidism is most often caused by destruction of the thyroid gland. In some cases the dog's own immune system attacks the gland. In other cases, the gland becomes damaged.
Poor Hair Coat
If your dog is eating a good quality diet but her hair coat is poor, it could be a sign of hypothyroidism. Look for brittle fur and excess shedding.
Unexplained Weight Gain
Active dogs that continue to gain weight may be suffering from low thyroid function. Feel around your dog's ribcage. If you can't feel his ribs, he's overweight.
Lethargy
Your dog's activity level should be appropriate to her breed. If she is not elderly but is showing signs of lethargy, consider a thyroid test.
Reddened Skin And Rat Tails
Red, scaly skin may be a sign of hypothyroidism. Flea bites and skin allergies will cause itchy patches, but low thyroid skin conditions do not itch. Some dogs lose tail fur, resulting in a hairless "rat tail."
Skin Discolorations
Hypothyroidism can cause black skin discolorations, particularly around the groin. The skin may become oily and thickened.
Susceptible Dogs
Medium and large dogs--particularly Golden Retrievers, Doberman Pincers and Cocker Spaniels--are more likely to suffer from this condition, and spayed females seem to be more at risk as well. It usually occurs between the ages of four and ten.
