DOGS · OWNER EDUCATION
Hypothyroidism in Dogs
Low thyroid hormone function can contribute to weight gain, low energy, skin or coat changes and other signs that overlap with many unrelated conditions.
THE SHORT VERSION
Understanding supports better veterinary conversations.
Canine hypothyroidism occurs when the thyroid gland does not provide adequate thyroid hormone for normal body function. Diagnosis requires appropriate testing because unrelated illness and medication can also alter thyroid results.
What is this condition?
Canine hypothyroidism occurs when the thyroid gland does not provide adequate thyroid hormone for normal body function. Diagnosis requires appropriate testing because unrelated illness and medication can also alter thyroid results.
Which animals can be affected?
Risk factors, examination findings and management can differ between species and individual patients.
Why can it happen?
- Primary thyroid gland dysfunction.
- Individual age, breed and immune-related factors may influence risk.
- Other illness can mimic thyroid disease or interfere with testing.
What might an owner notice?
- Weight gain without an obvious increase in food intake.
- Lethargy, decreased exercise tolerance or heat-seeking behavior.
- Hair thinning, recurring skin issues or coat changes.
How is the problem investigated?
- Veterinary history, physical examination and a carefully selected thyroid testing panel.
- Complete blood count and chemistry testing when additional context is needed.
- Review of medications and other illnesses before interpreting thyroid values.
What might treatment involve?
- Veterinarian-prescribed thyroid hormone replacement when diagnosis is supported.
- Scheduled follow-up testing to evaluate response and medication timing.
- Management of associated skin or weight concerns.
This is an overview, not a prescription or a recommendation for a specific individual animal.
What can owners do at home?
- Give medication exactly as prescribed and keep recheck appointments.
- Track energy, weight, coat condition and skin changes.
- Tell the clinic about supplements or other medications.
Avoid actions that could make care less safe.
- Do not give human medications, leftover prescriptions or supplements without veterinary approval.
- Do not stop, increase, decrease or double prescribed medication without contacting your veterinary team.
- Do not delay assessment if symptoms are worsening, the animal stops eating or an emergency sign appears.
What can the longer-term outlook involve?
Many appropriately diagnosed dogs improve with consistent treatment and monitoring; other contributing conditions may require separate care.
Can risk be reduced?
- There is no universal way to prevent hypothyroidism; early evaluation of persistent signs improves recognition.
When should you arrange care?
- Call for ongoing weight gain, lethargy, coat changes or unexpected response to medication.
Seek emergency veterinary care if you notice:
SEEK EMERGENCY VETERINARY CARE- Collapse, severe weakness, abnormal breathing or any rapidly worsening systemic illness.
Sources behind this guide
American Animal Hospital Association veterinary guidelinesPrimary veterinary or veterinary-university guidance ↗Content last reviewed: August 23, 2026. Review status: veterinary-informed; independent veterinarian review not yet completed.