Some pet parents gradually start to notice their pup is looking a bit pudgy. Others have the opposite problem, fretting over why Fido suddenly looks malnourished. Either way, fluctuations in weight along with other symptoms could indicate one of several thyroid issues.

While hypothyroidism is one of the most common thyroid problems in dogs, there are a few others that could be causing your pet grief. Here are four thyroid challenges dogs might experience.

1. Hypothyroidism

Hypothyroidism occurs when the thyroid gland doesn’t produce enough hormones. Dogs with this condition have low triiodothyronine (T3) and thyroxine (T4) levels, which leads to inhibited cell growth and a slow metabolism. Symptoms of hypothyroidism include lethargy, skin disorders, hair loss and weight gain despite a consistent feeding schedule.

The main cause of hypothyroidism in dogs is autoimmune lymphocytic thyroiditis. It’s a disorder in which the immune system develops antibodies to attack the dog’s natural thyroid tissue. In this case, the vet will prescribe treatment for the autoimmune disorder rather than hypothyroidism. Other instances of hypothyroidism are due to idiopathic atrophy, which means the thyroid gland stops functioning for no discernable reason.

Hypothyroidism is often treated with hormone replacement therapy. These medications include various levels of T3 and T4, with the dosage depending on the dog’s unique situation. Hypothyroidism is a lifelong illness with no known cure, but thyroid supplements or medication can help dogs live a normal, healthy life.

2. Hyperthyroidism

Hyperthyroidism is the complete opposite of hypothyroidism. The condition develops when a dog’s thyroid gland produces too many hormones. Excessive hormone levels circulating in the body result in accelerated metabolism and heart problems, such as enlargement, murmurs and heart failure. Other symptoms include weight loss, hyperactivity, increased appetite and thirst, shortness of breath and digestive problems. Hyperthyroidism is rare in dogs and often has a poor prognosis.

Hyperthyroidism in dogs is almost always caused by thyroid carcinoma. Thyroid carcinoma is a type of cancer that develops in the thyroid gland. Enlargement of the thyroid gland often indicates a cancerous tumor is present. However, swelling around the neck doesn’t always mean your dog has hyperthyroidism. Always speak with your vet to receive an accurate diagnosis.

Since hyperthyroidism stems from cancer, the thyroid condition is usually treated with chemotherapy and surgery to remove the tumor. The vet might also recommend hormone therapy to lower the T3 and T4 levels circulating within the body. Keep in mind that improving symptoms of hyperthyroidism doesn’t necessarily get rid of the underlying cause.

3. Autoimmune lymphocytic thyroiditis

As mentioned earlier, lymphocytic thyroiditis is an autoimmune disorder in which the immune system releases antibodies that attack healthy thyroid tissue. The immune system mistakes thyroid cells for pathogens and destroys them, making it difficult to produce adequate hormone levels. Hypothyroidism and autoimmune lymphocytic thyroiditis often share similar symptoms. However, it’s important to note that both conditions aren’t always present at the same time.

Autoimmune lymphocytic thyroiditis is often the result of lupus. Lupus is a systemic autoimmune disorder, meaning antibodies attack normal cells throughout the entire body. The thyroid gland is one of many systems that suffers from lupus, and your dog may experience deficiencies in other organs, as well.

Similar to hypothyroidism, autoimmune lymphocytic thyroiditis is a chronic condition that stays with a dog their entire life. Both thyroid conditions are treated the same way, usually involving consistent doses of thyroid hormones. Lifelong treatment helps the thyroid gland function normally so the dog can enjoy a heightened sense of wellbeing.

4. Enlarged thyroid gland

Enlarged thyroid glands are commonly referred to as goiters. Many pet parents are worried when they detect a goiter because they mistake it for a cancerous tumor. However, a swollen neck doesn’t always indicate thyroid carcinoma. Goiters are harmless and usually develop when the pituitary gland constantly signals the thyroid to ramp up or slow down hormone production.

A number of things lead to goiters in dogs. Both iodine deficiencies and too much iodine can lead to goiters, because the thyroid uses iodine to produce T3 and T4 hormones. Some goiters develop as a result of antibiotics or a genetic defect.

Small goiters can dissipate when the dog receives prescribed medication. Ones that are too large require surgical removal. Dogs have two thyroid glands, so removing one means the other is still present to supply the body with hormones. Vets can supplement the procedure with hormone replacement therapy to compensate for the missing thyroid gland.

The big takeaway is that most thyroid issues in dogs have a positive outcome. With the appropriate treatment plan, dogs afflicted by thyroid issues can reduce their symptoms and experience life like any normal pup.