Hyperthyroidism in dogs

It is often referred to as an 'overactive thyroid', is when the thyroid gland produces and secretes excessive amounts of the free - not protein bound and circulating in the blood. This is the opposite of hypothyroidism, which is the reduced production and secretion of T3 and/or T4. Very few dogs are diagnosed with hyperthyroidism. It is usually caused by cancer of the thyroid gland. The cancer tumour causes the thyroid to give off too much hormone. This disease usually affects older dogs. Hyperthyroidism may be asymptomatic, but when it is not, symptoms are due to an excess of thyroid hormone. Some of the symptoms of hyperthyroidism are nervousness, irritability, increased perspiration, heart racing, hand tremors, anxiety, difficulty sleeping, thinning of the skin, fine brittle hair, and muscular weakness. When a dog has too much thyroxin, it may lose weight even though it is eating the same amount of food. It may be hungry all the time and bolt its food until it vomits. The dog is often excessively thirsty. It can have diarrhoea and urinate much more often than normal. Major clinical signs include weight loss, anxiety, hair loss, muscle aches, weakness, fatigue, hyperactivity, irritability. Long term untreated hyperthyroidism can lead to osteoporosis. A dog with hyperthyroidism often is irritable and hyperactive because of the excess hormones. Its coat may look shaggy. Weight loss often causes the dog to be too thin and suffer muscle wasting. Though it is overly active at times, the dog may be weak due to the loss of muscle strength and its nervous physical activity.

HYPOTHYROIDISM IN DOGS

This is a disease of thyroid deficiency. Dogs with hypothyroidism have metabolic rates below normal. Hypothyroidism, in most cases, is caused by autoimmune thyroiditis (also called lymphocytic thyroiditis), which results in destruction of thyroid tissue. Autoimmune thyroiditis is known to be an inherited disease. The disease occurs most often in middle-aged dogs of medium and large breeds, but has been seen in virtually every breed and in mixed breeds as well. The breeds most commonly affected are the Golden Retriever, Doberman pinscher, Irish Setter, Miniature Schnauzer, Dachshund, Cocker Spaniel, Labrador Retriever, Greyhound. Hypothyroidism is the most common endocrine skin disease in dogs-but it is still less common than other skin diseases. Coat and skin changes are bilateral and symmetrical. A typical sign is poor hair regrowth, which is most noticeable after the dog has been clipped. . Other signs of hypothyroidism include weight gain, intolerance to cold, a slow heart rate, and absence of heat cycles, lethargy, and a variety of nonspecific symptoms. Hypothyroid dogs may develop blepharitis, corneal ulcers, deafness, constipation, and anaemia. At least two-thirds of hypothyroid dogs have high serum cholesterol levels. Behaviour changes including aggression have also been noted in hypothyroid dogs, particularly German Shepherd Dogs. The recommended blood test for screening purposes is the total T4. A normal T4 is fairly conclusive evidence that the dog does not have hypothyroidism. However, a low-normal or below-normal level does not mean the dog is hypothyroid, because concentrations below normal are common for many reasons other than hypothyroidism.

CANINE THYROID DISEASES

Canine thyroid disease can be tough to diagnose. The symptoms can be: lethargy, weight gain, dull coat, skin infections, constipation, diarrhoea, cold intolerance, skin odour, hair loss, dry skin, reproductive problems, aggression, and more. The associated conditions can be serious: mega-oesophagus, ruptured knee ligaments, testicular atrophy, excessive bleeding, and corneal ulcers. The disease can be inherited or of unknown origin. Thyroid gland Endocrine glands secrete hormones that help manage the body’s processes. The thyroid gland lies on the dog’s trachea, just below the larynx; tri-iodothyronine and levo-thyroxine, the hormones produced by the thyroid, govern the body’s basic metabolism — including control of growth and development and maintenance of protein, carbohydrate, and lipid metabolism — throughout life. The most common cause of canine thyroid disease is autoimmune thyroiditis. It is an immune-mediated process that develops in genetically susceptible individuals and is characterized by the presence of anti-thyroid antibodies in the blood or tissues. Thyroiditis is believed to start in most cases around puberty, and gradually progress through mid-life and old age to become clinically expressed hypothyroidism once thyroid glandular reserve has been depleted. During this process, the animal becomes more susceptible to immune-mediated or other diseases affecting various target tissues and organs.