- 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.
- 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.
- 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.
- 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.
- 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."
- Hypothyroidism can cause black skin discolorations, particularly around the groin. The skin may become oily and thickened.
- 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.
