Introduction
Hypothyroidism is a clinical syndrome caused by abnormally low circulating levels of blood thyroid hormones, called T3 (triiodothyronine) and T4 (thyroxine). It is a relatively common problem usually found in middle-aged dogs (2-6 years of age) of both sexes and often is accompanied by vague, nonspecific symptoms that mirror those of other diseases. Once hypothyroidism is diagnosed definitively by a veterinarian, it can be treated fairly easily, although treatment must continue for the dog’s lifetime.
Treating Hypothyroidism
Hypothyroidism is a chronic disorder that generally does not require any sort of acute or emergency care. While it normally requires treatment for the rest of a dog’s life, the condition can be treated with relatively affordable daily oral medication, which will reverse all of the clinical abnormalities associated with the disease. The goal of treatment is to return blood thyroxine levels to normal and to minimize (or hopefully eliminate) all clinical signs of the disorder. With proper and consistent daily treatment, almost all dogs with hypothyroidism can go on to lead long, healthy and normal lives.
The effects of hypothyroidism in dogs are caused by the thyroid’s failure to produce the proper levels of thyroid hormones. Treatment is usually accomplished by giving daily doses of a synthetic T4 thyroid hormone called sodium levothyroxine, in the form of oral tablets. Successful treatment is dependent on maintaining proper thyroxine levels in the dog’s blood. The frequency of dosing will depend upon the dog, but most protocols call for either once or twice daily treatments. The treating veterinarian should periodically test the dog’s blood to make sure that thyroxine levels are being brought up to and maintained at normal levels. These tests will be more frequent at first (maybe every 4-6 weeks), and will decrease in frequency as thyroid levels are stabilized.
Dog owners can expect to see dramatic improvement in their dogs within the first 1-2 weeks of treatment. Normally, energy and an interest in activities return first, and the dog just seems to be feeling better. Dermatologic and neurologic signs improve over several months, with hair regrowth, improved overall skin condition and improved tolerance to exercise and general function. With time, a healthy diet and exercise, weight loss can be achieved as well. Reproductive abnormalities can take a bit longer to resolve, but should do so.
If major clinical improvement is not seen in a dog within 3 months of thyroxine treatment, despite normal blood levels of thyroid hormones as monitored during treatment, the diagnosis of hypothyroidism in probably incorrect and another underlying cause for the clinical signs must be explored.
Dogs suffering from hypothyroidism can be anesthesia risks, so additional precautions should be taken by the veterinary team prior to anesthetic induction. These dogs tend to get inordinately cold when under general anesthesia (becoming “hypothermic”), and because of their altered metabolism the anesthetic agents frequently have a more pronounced and long-lasting effect.