If your dog has been putting on a few extra pounds, it’s easy to assume he just needs more exercise. But sometimes weight gain has nothing to do with activity — and one possible cause is hypothyroidism, a medical condition that requires veterinary care.
Here’s how to tell whether your dog might be dealing with hypothyroidism and what you should know about this common condition.
What Is Hypothyroidism?
Hypothyroidism occurs when the thyroid gland doesn’t produce enough thyroxine — the hormone that regulates metabolism. With too little thyroxine circulating in the body, your dog’s metabolic rate slows down, leading to weight gain and other changes.
The condition is fairly common in dogs. While any breed can develop it, hypothyroidism is seen more often in medium and large dogs and in certain breeds like golden retrievers, Doberman pinschers, miniature schnauzers, cocker spaniels, Airedale terriers and Irish setters. It also most commonly affects middle-aged pups.
What Causes Hypothyroidism in Dogs?
Most cases stem from one of two underlying issues:
• Lymphocytic thyroiditis
This immune-mediated disease occurs when your dog’s immune system mistakes the thyroid gland for something harmful and begins attacking it.
• Idiopathic thyroid gland atrophy
In this form, the thyroid tissue is slowly replaced with fat for unknown reasons.
Less commonly, hypothyroidism can be caused by:
- Pituitary gland tumors
- Congenital thyroid defects (dogs born with an underactive thyroid)
Symptoms of Hypothyroidism in Dogs
Because thyroid hormones affect so many systems in the body, symptoms can vary — but common signs include:
- Weight gain without increased appetite
- Decreased appetite
- Low energy or reluctance to exercise
- Coat changes (dullness, thinning, excessive shedding)
- Skin darkening
- Hair loss
- Muscle weakness
- Abnormal heart rhythm
- Digestive issues
In more advanced cases, the skin on your dog’s face may thicken, giving him a puffy look or droopy eyelids. Dogs born with thyroid issues may also show signs of dwarfism due to the thyroid’s role in growth and development.
How Is Hypothyroidism Treated?
The good news: hypothyroidism is very manageable.
Treatment involves giving your dog a synthetic thyroid hormone called levothyroxine. Because the disease is chronic, this medication will be part of your dog’s routine for life — but once treated, most dogs feel dramatically better.
Dogs who receive consistent therapy have an excellent prognosis and typically live a completely normal lifespan.
Since lifelong medication and monitoring can add up, pet insurance can help cover costs — but be sure to enroll before any diagnosis, since hypothyroidism becomes a pre-existing condition once noted in your dog’s medical record.
The Bottom Line
A hypothyroidism diagnosis isn’t a reason to panic. With the right treatment, your dog can live a happy, healthy, normal life. If you notice signs like weight gain, low energy or changes in coat and skin, check in with your vet — early detection means an easier path back to feeling good.
