Hypothyroidism in dogs
- Hypothyroidism is a lack of thyroid hormones due to underactive thyroid glands.
- Symptoms of hypothyroidism include weight gain, low energy, and fur loss (alopecia).
- Hypothyroidism is treated using daily medication to replace the missing thyroid hormones.
- With treatment, the outlook for a dog with hypothyroidism is excellent.
- Contact your vet if your dog is showing signs of hypothyroidism.
The thyroid glands are two small glands that sit in the neck, close to the windpipe.
They produce thyroid hormones that are used all around the body.
Hypothyroidism is a condition that develops when the thyroid glands become underactive and don’t produce enough thyroid hormones.
Hypothyroidism is the opposite of hyperthyroidism – a condition caused by overactive thyroid glands producing too much thyroid hormone (common in cats but very rare in dogs).
Symptoms of hypothyroidism are usually vague and develop gradually; common signs include:
- Unexplained weight gain (or difficulty losing weight)
- Fur loss (alopecia) on the neck and sides
- ‘Rat tail’ - fur loss on the tail
- Low energy (lethargy)
- Dry, flaky skin (dandruff)
- Skin infections
- Thick skin around the face and a ‘sad’ expression
- Struggling to keep up on walks
- Feeling cold (you may notice shivering)
- Coma (in severe cases).
Outlook and ongoing care
With successful treatment, your dog’s outlook is excellent. As long as they stay on treatment, they can live a long, happy life without symptoms.
How long does thyroid medicine take to work?
Your dog should seem happier and more energetic within a couple of weeks. They may lose more fur to begin with but don’t worry, this is normal, it should start to regrow within 4-6 weeks. They should be looking slimmer and healthier within 3 months and be back to normal within 6 months.
Your dog will need regular vet checks, and you will need to monitor for any new symptoms. Your vet may perform repeat blood tests to ensure your dog’s thyroid hormones are staying at the right level.
What happens if hypothyroidism is left untreated?
If you leave your dog’s hypothyroidism untreated, they will continue feeling poorly and their symptoms will get worse. Eventually severe complications will develop which may lead to death.
What’s the difference between ‘hypothyroidism’ and ‘hyperthyroidism’?
- Hypothyroidism = low levels of thyroid hormone (common in dogs, rare in cats).
- Hyperthyroidism = high levels of thyroid hormone (common in cats, rare in dogs).
What’s the best dog food for hypothyroidism?
Hypothyroidism nearly always causes weight gain in dogs. However, once your dog has started treatment, their metabolism will return to normal and they will lose those extra pounds. It’s unlikely you will need to change your dog’s diet.
Treatment for a chronic condition such as hypothyroidism can become very expensive over time. Consider insuring your dog as soon as you get them, before any signs of illness start. This will ensure you have all the support you need to care for them.
It’s also very important to speak openly to your vet about your finances, the cost of treatment, as well as what you think is right for your dog. There are often several treatment options so if one doesn’t work for you and your pet then the vet may be able to offer another.
Published: August 2019
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Written by vets and vet nurses. This advice is for UK pets only.
Illustrations by Samantha Elmhurst