Hypothyroidism in Dogs: Diagnosis, Care & Supportive Supplements.

A real-world case from an Ace Canine customer

We recently received a great question from an Ace customer. Her 2-year-old Border Collie, an active agility and hoopers dog, was recently diagnosed with hypothyroidism. Naturally, she wanted reassurance that Ace Canine joint care supplements like FlexSprinkle would be safe to use alongside thyroid medication.

What is Hypothyroidism in Dogs?

Hypothyroidism is a common endocrine disorder where the thyroid gland fails to produce adequate thyroid hormones, especially thyroxine (T4). These hormones are essential for regulating metabolism, energy levels, and organ function.

The most frequent cause is autoimmune thyroiditis—the dog’s own immune system attacks the thyroid gland. In some cases, the gland atrophies over time. The condition is typically seen in middle-aged or older dogs, though young dogs, like in this case, can also be affected. Certain breeds, including Golden Retrievers, Doberman, and Cocker Spaniels, are more susceptible.

Common Signs and Symptoms

Hypothyroidism develops gradually, and symptoms may be subtle at first. Key signs include:

·       Lethargy or reduced stamina

·       Weight gain despite a normal diet

·       Thinning coat or patchy hair loss (alopecia)

·       Cold intolerance

·       Slowed heart rate

·       Reproductive issues (in intact dogs)

·       Behavioural such as depression or anxiety

How Is It Diagnosed?

Vets confirm hypothyroidism using a combination of:

1.    Clinical history and signs

2.    Blood tests, including:

Total T4
Free T4 (active form) 
TSH (thyroid-stimulating hormone)

A classic diagnostic profile shows low T4 and free T4, with high TSH.

Treatment: Levothyroxine (Thyforon)

The standard treatment is levothyroxine, a synthetic T4 hormone replacement.

In the UK, Thyforon is a common brand administered once or twice daily, depending on your vet’s guidance

The dosage is adjusted over time based on weight and blood test results. Most dogs show improvement within a few weeks, including energy, coat health, and weight stability.

Supporting Wellness:
Supplements, Diet & Immunity - What Should Hypothyroid Dogs Eat (or Avoid)?

Nutrition can support thyroid balance and manage symptoms.

Avoid: Excess iodine (e.g., kelp, seaweed) — can interfere with hormone regulation

Soy-based ingredients — may impair hormone absorption

Raw cruciferous vegetables (broccoli, kale, cauliflower) — contain goitrogens

High-fat diets — worsen weight gain and fatigue

Include: Lean proteins — help preserve muscle mass

Omega-3 fatty acids — reduce inflammation and support skin/coat

Whole grains and veggies — for fibre and metabolic balance

Controlled iodine — found in balanced dog foods and FlexSprinkle

Always consult your vet before making dietary changes—especially for dogs on levothyroxine

Can Biotics Help Dogs with Autoimmune Disease?

Absolutely. Hypothyroidism in dogs often has autoimmune origins, and the gut plays a vital role in immune regulation.

The gut microbiome helps regulate inflammation and immune tolerance Probiotics can improve gut flora and support the immune system.

Postbiotics, like those in Epimmune by Ace Canine, are advanced alternatives—ready-made beneficial compounds produced by probiotics. Unlike probiotics, they’re not degraded by stomach acid and offer direct immune and gut-modulating benefits.

This makes gut health a crucial pillar in managing autoimmune hypothyroidism.

Supplement Spotlight

FlexSprinkle: Joint support with Green Lipped Mussel anti-inflammatory containing natural glucosamine and chondroitin and safe levels of iodine—ideal for long-term use in hypothyroid dogs.

Phylax: A cartilage-supportive supplement that may reduce joint wear over time- especially recommended in young dogs or breeds with known joint challenges.

Epimmune: Gut and immune support via postbiotics—especially relevant for autoimmune-prone dogs.

All three are safe to use alongside levothyroxine, offering a well-rounded care plan.

Call or email with questions about hypothyroidism or anything else.  

support@ace-canine.com

0118 9842871