Hypothyroidism

T3hypo — Thyroid gland not producing enough thyroid hormone--hypothyroidism.

This is the medical term for an underactive thyroid gland. One of the many things the thyroid gland is responsible for is to regulate metabolism. When not enough thyroid hormone is secreted, the metabolism slows^[1]; secreting too much results in hyperthyroidism and a too-rapid metabolism. The thyroid gland is actually controlled by another gland, the pituitary gland. It signals the thyroid to produce its hormone and is responsible for the amount of thyroid hormone in the blood.

Symptoms[]

Symptoms of hypothyroid are dry skin and coat, often a loss of hair at the rear portion of the body, sluggishness and weight gain even if the animal has his/her meals reduced, skin that is cold to the touch. The animal may also deliberately seek out warm places to lie. Forms of neuropathy can result from hypothyroidism^[2], because it is an endocrine disease.

Causes[]

In many hypothyroid cases, the true cause of the lack of thyroid function is never discovered--it's referred to as idiopathic hypothyroidism. The other is known as lymphocytic thyroiditis, where the body begins producing antibodies against the thyroid gland.

Symptoms of hypothyroidism may not develop until 75% of the thyroid gland is destroyed; it may take 1-3 years from development of the condition to this point. Idiopathic and lymphocytic thyroiditis causes account for over 95% of hypothyroidism in dogs^[3].

In less than 10% of hypothyroidism cases, the problem is not with the thyroid gland itself, but with the pituitary gland in the brain. The pituitary gland produces a thyroid stimulating hormone (TSH)^[4]; without this hormone to signal the thyroid gland to produce its thyroid hormone, the thyroid gland remains inactive^[5].

Lack of iodine in the pet's diet can result in insufficient production of thyroid hormones with the result being a type of hypothyroidism^[6].

Treatment[]

Treatment is to replace the missing thyroid hormone, which will need to be done for life. With proper continuing treatment, a normal life is expected. Intervet has introduced a new oral liquid replacement therapy called Leventa. Unlike tablet replacement treatments, which need to be given twice daily, Leventa is able to be given only once a day^[7].

Hypothyroidism and diabetes[]

Dogs who also have diabetes have problems with regulation when their thyroid is underactive^[8]. Treating the thyroid condition with replacement therapy--natural or synthetic thyroid hormone often resolves the diabetic regulation problem in the process. There's more than one test to determine thyroid function^[9]^[10].

Hypothyroidism can cause Insulin resistance-meaning more insulin needed^[11], but it can also decrease the body's metabolic rate. If this is the case, the decrease in the metabolism would reflect as decreased insulin requirements^[12].

References[]

[1] Canine Hypothyroidism

[2] Canine Hypothyroidism-Southpaws.com

[3] Intervet-Leventa-Hypothyroidism Treatment

[4] Thyroid-Stimulating Hormone-College of Veterinary Medicine-Colorado State

[5] Intervet-Leventa-Hypothyroidism Treatment

[6] Drs. Foster & Smith-Iodine Requirements in Dogs

[7] Leventa.com

[8] Insulin Resistance in Three Dogs With Hypothyroid & Diabetes Mellitus-Journal of the American Veterinary Association (JAVMA)-1993

[9] Canine Hypothyroidism-Dechra-US

[10] Intervet-Leventa Diagnostic Protocol-Canine Hypothyroidism

[11] Effect of Hypothyroidism on Insulin Sensitivity in Dogs-ACVIM 2008 Oral Presentations-Page 29, Abstract #94

[12] Better Medicine E-Newsletter-June 2006

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