Dog Hypothyroidism: Common Endocrine Condition and Management

Hypothyroidism is the most common endocrine disorder in dogs and highly treatable, making early recognition and lifelong management central to welfare for affected breeds.

Key Facts

Hypothyroidism affects approximately 1 in 156 dogs, most commonly mid-sized and large breeds
Golden Retrievers, Doberman Pinschers, and Irish Setters have elevated genetic risk
Classic signs include weight gain without dietary change, lethargy, cold intolerance, and dull coat
Daily oral levothyroxine supplementation provides complete or near-complete resolution of symptoms
Diagnosis requires measuring total T4 and free T4 alongside TSH for accurate assessment

Welfare Considerations

Untreated hypothyroidism causes progressive obesity, lethargy, and poor coat quality that significantly reduces quality of life. The condition is entirely manageable with inexpensive daily medication — levothyroxine costs pennies per day for most dogs. Early diagnosis before obesity develops prevents the cascade of secondary welfare problems including joint disease and metabolic syndrome. Annual thyroid monitoring after dose stabilization ensures continued effective control.

What You Can Do

Include thyroid testing in annual wellness panels for at-risk breeds from middle age
Recognize weight gain without dietary change and lethargy as hypothyroidism indicators
Administer levothyroxine consistently at the same time daily for best absorption
Monitor response to treatment including weight, energy, and coat quality improvements