Hypothyroidism
The thyroid glands are located in the neck on either side of the trachea (windpipe). These glands require sufficient quantities of iodine for normal production of the thyroid hormone. The thyroid hormone effects the metabolism of all tissues, particularly the metabolic rate. It is required for normal growth and development. The disorders of the thyroid glands are:
HYPOTHYROIDISM, which causes a reduced metabolic rate. Iodine deficiency can lead to cretinism in the young; thickening and swelling of the skin, called myxedema in adults; and goiter, which causes enlargment of the thyroid gland.
The exact cause of hypothyroidism is not always evident or understood. The disease is most commonly seen in four- to six-year-old, medium to large breeds of dogs. Miniature or toy breeds are seldom affected.
SIGNSThe signs of hypothyroidism ar"e lethargy, increased appetite, weight gain, loss of libido, infertility, sensitivity to cold, a brittle, dry, dull haircoat, loss of hair especially over the neck, back, and tail areas, and in some cases an oily skin and escessive wax in the ears; chronic skin infections. Any dog with cronic skin infections should be tested for hypothyroidism. As the disease advances, the skin darkens in color, thickens, and feels cool to the touch. The dog becomes more dull and irritable, and heart problems may develop. Only about 50% of hypothyroid dogs show the skin and hair changes.
Clinical disturbances associated with hypothyroidism vary among affected animals and not
every sign is seen in each animal patient. Many clinical signs associated with hypothyroidism
are due to a reduction in basal metabolic rate. A gain in body weight without an associated
change in appetite occurs frequently. The weight gain may vary from slight to striking obesity.
The animal usually is less active and the owner may observe a reluctance to play or take walks.
The inactivity also contributes to the weight gain. Dogs with hypothyroidism may have
difficulty in maintaining normal body temperature and are often heat seekers. They will lie on
or near sources of heat, such as registers, radiators, and electric blankets, and be reluctant to venture outdoors in cold weather. Excessive shivering may be observed and the skin frequently
feels cool.
In case of congenital hypothyroidism of Toy Fox Terriers, there is delayed ear and eye opening, palpable goiter (enlarged thyroid gland to
compensate for decreased production), stunted growth, mental dullness.
TREATMENT Treatment involves the use of replacement thyroid hormone drugs, usually for life. Establishing the dosage requires veterinary supervision and periodic monitoring of the affected dog is absolutely necessary. If the diagnosis is correct, the prognosis is good. Many dogs have increased activiity in 10 days; hair regrows in 4-6 months and other signs improve in 2 months.
CAUTION: Because vegetables such as broccoli and cabbage can depress thyroid hormones if eaten in large amounts, they should not be fed to dogs with hypothyroidism.
Dog breeds that are predisposed to hypothyroidism
Metabolism—the process by which foods are transformed into basic elements which can be utilized by the body for energy or growth.
Lethargy—inactivity; drowsiness; forgetfulness.
Adapted from
1. Thyroid Disorders in Animals. Charles C. Capen
2. Hypothyroiidiism. Dr. Sandy Merchant
Go Pets America recommends seeking the advice of your local veterinarian for the most appropriate vaccination program and for the diagnosis and treatment of your pet's health problems. For vaccination requirements please contact your state and local licensing authorities.
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