📉 Hypothyroidism in Dogs – A 2025 Vet’s Guide to Recognizing and Managing an Underactive Thyroid

By Dr Duncan Houston, BVSc

🔍 What Is Hypothyroidism?

Hypothyroidism occurs when the thyroid glands in a dog’s neck produce insufficient thyroid hormone. This hormone regulates metabolism, energy, skin health, and many other internal processes. When hormone levels drop, a wide range of physical and behavioral symptoms can occur. 🐶⚖️

📊 Who Is Affected?

• Typically seen in middle-aged to older dogs
• Often misdiagnosed or mistaken for aging or obesity

💡 Common Signs of Hypothyroidism

Because thyroid hormones affect so many body systems, signs of hypothyroidism are varied and may develop gradually:

• 😴 Fatigue, dullness, or lethargy
• 🌡️ Seeking warm places or intolerance to cold
• 📉 Weight gain or “puffiness” despite normal diet
• 🐕 Hair thinning, poor coat quality, or dry skin
• ⚫ Darkened, thickened, or flaky skin
• 💤 Excessive sleeping
• 🐾 Poor wound healing or recurring skin infections

Hair loss is often symmetrical and most noticeable in areas of friction (e.g., flanks, tail base, and neck). Regrowth of clipped hair may also be delayed. 🧬

🧪 How Is Hypothyroidism Diagnosed?

Diagnosis relies on blood testing to evaluate thyroid hormone levels. No single test is perfect, so your vet may recommend one or more of the following:

• 🩸 Total T4 – Measures all circulating T4 hormone
• 🧪 Free T4 – Measures the biologically active form of the hormone
• 🧠 TSH (thyroid-stimulating hormone) – Elevated levels can indicate underactive thyroid glands
• ⚡ TSH stimulation test – A more involved test for challenging cases

Sometimes, testing must be repeated to confirm a diagnosis. Certain illnesses and medications can temporarily suppress thyroid hormone levels. 🧪

💊 Treating Hypothyroidism

There is no cure for hypothyroidism, but it is very manageable with daily medication. Dogs are treated with a synthetic thyroid hormone (levothyroxine), usually given as a tablet once or twice daily. 💊

⏱️ What to Expect

• 🐕 Increased energy in 1–2 weeks
• 📉 Weight loss and improved coat in a few months
• 🌟 Skin and coat may take 3–6 months to fully improve

💡 Regular blood testing is required to monitor hormone levels and adjust dosage. Never change the dose without your vet’s guidance.

⚠️ Signs of Overmedication

If your dog receives too much thyroid hormone, symptoms of hyperthyroidism may appear:

• ❤️ Rapid heart rate
• 🧃 Excessive thirst or urination
• 😠 Restlessness or behavior changes
• ⚖️ Unexpected weight loss

Always report new symptoms to your veterinarian promptly. 🩺

🔄 Long-Term Outlook and Monitoring

Hypothyroidism is a lifelong condition. With the right dose of medication and routine bloodwork, most dogs do extremely well and live normal, active lives. 💚

Recommended Follow-Up Schedule:

• 📆 Every 4–6 weeks initially (while adjusting dose)
• 📅 Every 6–12 months once stable

🐾 Ask A Vet for Support

If you suspect your dog may have hypothyroidism—or if you’re navigating medication and test results—the Ask A Vet App is here to help. Get expert advice, dosage guidance, and support anytime. 🐶📱

Visit AskAVet.com or download the app for real-time vet support, tailored to your dog’s needs. 🩺

✅ Summary: Key Takeaways

• 📉 Hypothyroidism = low thyroid hormone production
• 🧬 Symptoms: lethargy, weight gain, coat changes, cold intolerance
• 🧪 Diagnosed via blood tests (T4, free T4, TSH)
• 💊 Treated with lifelong thyroid hormone pills
• 📅 Regular vet checks ensure correct dosing

💬 Final Words from Dr Duncan Houston

Hypothyroidism in dogs is common, treatable, and manageable. With proper diagnosis, regular monitoring, and consistent medication, your dog can feel energized, look great, and enjoy every day to the fullest. 🐶💙

Need help interpreting results or adjusting medication? Connect with us anytime through the Ask A Vet App or at AskAVet.com. We’re with you every step of the way. 🐾📱