Canine Hypothyroidism

Hypothyroidism is a common disorder in middle-aged to older dogs characterised by a reduction of thyroid hormone production. Many breeds are commonly affected by this disease, for example: Boxers, Cocker Spaniels, Golden Retrievers, Labs, Poodles, Dachshunds and Miniature Schnauzers. It is likely that some breeds are genetically predisposed. There is no difference in frequency of occurrence between males and females.

Thyroid hormones affect almost every organ in the body and thus many signs of this disease are common. These include lethargy, depression, obesity despite normal feeding amounts, hair loss, skin and ear infections, weak or torn knee ligaments. Should this disease be suspected initial screening bloodwork is performed. Dogs that are hypothyroid have thyroid levels that are almost always below the normal range.

Supplementation of thyroid hormone by pills is the treatment for hypothyroidism. In general twice a day administration for 6-8 weeks is started. Most dogs show marked improvement in activity levels within 1 month of beginning therapy. Improvement in skin and a reduction in body weight may not be observed for several months. Retesting the thyroid levels 6-8 weeks after starting therapy is recommended and d dosage adjustment is made if necessary. Supplementation is for life.

Excessive administration of thyroid supplement rarely occurs. Side effects may include hyperactivity, ravenous appetite and weight loss. Signs resolve within 1-3 days of stopping treatment and re-evaluation and dosage adjustment is usually necessary.

The long term prognosis for dogs with hypothyroidism is good to excellent. Clinical signs and laboratory abnormalities are reversible with appropriate treatment. Some dogs are effectively managed on a once a day dose.