Introduction
Hypothyroidism is one of the most common hormonal disorders in dogs, but diagnosing it accurately can be tricky, especially when early signs are subtle or hidden. A new long-term study funded by the AKC Canine Health Foundation sheds light on a condition called subclinical thyroiditis, helping dog owners and veterinarians better understand which dogs are at risk of developing full-blown hypothyroidism (Grant 02659: Breed Specific Reference Ranges for Canine Thyroid Testing).
This breakthrough matters because it helps prevent misdiagnosis and ensures dogs get the right care at the right time. If your dog has abnormal thyroid test results but no symptoms, this research could directly impact their health monitoring and treatment plan.
Key Points
- Subclinical thyroiditis shows abnormal thyroid antibodies but normal hormone levels.
- About one-third of affected dogs will develop clinical hypothyroidism over time.
- Most dogs continue to show abnormal thyroid test results long-term.
- Annual monitoring is recommended for dogs with subclinical thyroiditis.
- Breed, medications, and other illnesses can affect thyroid hormone levels.
Challenge Background
Hypothyroidism in dogs is often overdiagnosed, leading to unnecessary treatment. The condition is typically identified by low thyroid hormone levels and symptoms like lethargy, weight gain, and coat changes. However, some dogs show abnormal antibody levels without any symptoms or hormone imbalances, a condition known as subclinical thyroiditis.
This creates a diagnostic challenge: should these dogs be treated, monitored, or left alone? Without long-term data, veterinarians and dog owners have struggled to make informed decisions.
The Breakthrough
Researchers at Michigan State University conducted a long-term study of 125 dogs from 31 breeds. These dogs had subclinical thyroiditis—elevated thyroid antibodies (TgAA) but normal hormone and TSH levels.
Over 2 to 9 years, researchers tracked hormone levels and clinical signs. They found that:
- Most dogs continued to show abnormal thyroid test results.
- About 33% progressed to clinical hypothyroidism requiring treatment.
- Only a few dogs returned to normal thyroid function.
This study provides critical evidence for how subclinical thyroiditis behaves over time and helps guide monitoring and treatment decisions.
Impact & Next Steps
Studies like this refine our understanding of hypothyroidism – the most over diagnosed hormonal disease in dogs. They emphasize the importance of monitoring dogs with subclinical thyroiditis at least once a year or more often if clinical signs of hypothyroidism develop and provide scientifically sound information that guides our diagnostic and treatment decisions. Because thyroid hormone levels are influenced by disease outside of the thyroid gland, the administration of certain medications, and a dog’s breed, it is important for veterinarians and dog owners to have this evidence. CHF and its donors remain committed to funding studies that provide this evidence and have a real impact on the health of our beloved dogs. Learn more at akcchf.org/research.
