Hypothyroidism is the most common hormonal disease seen in dogs. The thyroid gland is a butterfly shaped organ located just below the voicebox. Its main function is to regulate the body's metabolism. It is now believed that over 90% of all canine hypothyroidism is due to the body's own immune system attacking the thyroid gland and eventually rendering it useless (autoimmune thyroiditis). Clinical symptoms will only begin to appear once the thyroid gland's secretions are depleted to the point where it can't maintain metabolic functions. It's a gradual process with noticeable signs being seen between 2 years to middle age.
The symptoms can be variable but usually include: lethargy/mental dullness; hair loss primarily on the body and tail; weight gain (even when on a strict diet); dry hair coat; thickening, scaling and hyperpigmentation of the skin; cold intolerance and slow heart rate.
**Breeders will notice reproductive problems in both the males and females.
If hypothyroidism is suspected there are blood tests available (T3, T4 and TSH Stimulation test) that can diagnose the condition.
Once diagnosed, treatment is easy. It is simply a matter of putting the dog on daily synthetic thyroid hormone medication. Usually once the dog is on the medication for a few weeks, most of the clinical symptoms will resolve themselves and the dog will live a normal lifespan.
Unfortunately for breeders, it appears that there is a genetic susceptibility to developing hypothyroidism. Even though easily treated, dogs with hypothyroidism should not be used for breeding. If a case of hypothyroidism does show up in a breeder's line, it would then be prudent to test and screen all relatives before breeding.
For breeders, along with the standard diagnosing tests, there is a special screening blood test to check for the presence of antithyroid antibodies. If the antibodies are found, this means the thyroid gland is under attack by the body. It also signifies that the dog has the genetic form of hypothyroidism and even though the dog may not be exhibiting clinical symptoms as yet, that dog should not be used for breeding.
The Orthopedic Foundation for Animals (OFA) does thyroid certification and has a list of approved lab facilities that do the antibody test. (All diagnostic labs do not do it).
There is some question as to the prevalence of hypothyroidism in Maltese, but it is something that does occur from time to time in the breed.