Hypothyroidism in dogs

Hypothyroidism is a common hormonal disease in dogs. It is caused by an underactive thyroid gland. It is more common in middle-aged dogs and can be in any breed.

Symptoms are non-specific but usually consist of lethargy, inactivity, and weight gain. Sometimes symmetrical loss of hair on the body without any itching, or a dull coat can be noticed. Recurrent skin infections are also possible. Some animals will heat seek and often found snuggled right up to a radiator!

Diagnosis is based on clinical signs and results of blood tests.
A blood test for T4 (thyroid levels) which comes back low may increase clinical suspicion of hypothyroidism, and to confidently diagnose hypothyroidism further blood tests for TSH(thyroid stimulating hormone) and fT4 (freeT4) may be necessary.
Sometimes other illnesses can cloud the picture and falsely lower T4 which is why it is important to look at other tests and the clinical picture to reach a definitive diagnosis.

This diagram illustrates the testing process for hypothyroidism.

Treatment involves supplementing the body with thyroid hormone (levothyroxine) for the entirety of your pet’s life. We will initiate a baseline dose of the treatment.  Certain symptoms may take a few weeks to improve but coat quality may take several months.

The treatment can be in a tablet (Thyforon) or liquid formulation (Leventa).

4 weeks after starting levothyroxine a blood sample is required to ensure sufficient levels of thyroid hormone are being supplemented and equally not too much is being given. The blood test needs to be taken 4-6 hours after giving the dose of levothyroxine. Depending on the results the dose may need to be adjusted in small increments to find the perfect amount to supplement. Once the perfect dose has been established then regular monitoring of this every 6 months is recommended.

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