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Hypothyroidism in your Pet

The thyroid gland is located in the neck near the larynx and produces thyroid hormone in all mammalian species.

Thyroid hormone is important for the maintenance of normal body metabolism. A deficiency of thyroid hormone can be evident in a number of ways: weight gain, lethargy, heat-seeking, hair loss, greasy skin, recurrent skin infections, etc. Hypothyroidism occurs most frequently in middle-aged or older dogs although it can appear at a much younger age in larger dogs.

A resting thyroid hormone level measuring the circulating level of the hormone is initially tested. If the resting thyroid is low this can indicate hypothyroidism or may suggest suppression of thyroid hormone secondary to another illness.
To definitively diagnose hypothyroidism further testing of the free T4 (functional thyroid hormone) and thyroid stimulating hormone (TSH) is required. A hypothyroid patient will have a low free T4 and an elevated TSH. Usually these tests can be added onto the initial blood test.

Thyroid hormone deficiency is treated by using a synthetic hormone replacement. Because of the higher metabolic turnover of thyroid hormone in dogs, they require much higher and more frequent dosages when compared to humans. Once the diagnosis of hypothyroidism has been made, treatment is needed for the rest of the dog’s life.

Your dog will be treated with L-thyroxine at the dose of ___________ mg given twice daily.
It is necessary to recheck the thyroid level _____ weeks after initiation of therapy to make sure that your pet is being given the proper dosage. The blood sample will be taken _____ hours after the medication is given.

Personality changes are usually seen within 1 to 2 weeks. Coat changes are seen in about 4 to 8 weeks.