Hypothyroidism in dogs has the same effects as it does in humans, so for a good quality of life, the dog will need a synthetic thyroid hormone replacement, such as thyroxine.

Left untreated, the symptoms of hypothyroidism include hyperpigmentation, cold intolerance, slow heart rate, high cholesterol, slowed mental function, dry coat and skin, fur loss, weight gain and lethargy. These symptoms are resolved with the thyroid replacement medication.

If your dog is hyperactive, it may be that the dosage needs to be adjusted. The medication should alleviate the symptoms but should not cause new symptoms to arise (By the way, I have hypothyroidism, and without the correct hormone level I experience these symptoms as well and my quality of my life is poor). Consult with your veterinarian about the dosage. -PCT