Peer-reviewed veterinary case report
Thyroid problems in horses - diagnosis and treatment options
By Bertin, François-René et al.·Published in Equine veterinary journal·2024·School of Veterinary Science at The University of Queensland, Australia·View original on PubMed →
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Original publication title: Diagnosis and management of thyroid disorders and thyroid hormone supplementation in adult horses and foals.
- Species:
- horse
Plain-English summary
Thyroid problems in horses can be tricky to diagnose because many factors can affect how their thyroid works, and horses can actually live without a thyroid gland. While older horses often develop benign (non-cancerous) thyroid tumors, serious conditions like hypothyroidism (low thyroid hormone) or hyperthyroidism (high thyroid hormone) are quite rare. It's a common misconception that symptoms like being overweight, very tired, and not performing well in horses mean they have hypothyroidism, similar to what is seen in dogs and humans. In fact, low thyroid hormone levels in horses often happen due to other health issues rather than true hypothyroidism. Although real cases of hypothyroidism are uncommon, veterinarians often use thyroid hormone supplements to help manage weight and performance issues in horses.
Abstract
Equine thyroid disorders pose a diagnostic challenge in clinical practice because of the effects of nonthyroidal factors on the hypothalamic-pituitary-thyroid axis, and the horse's ability to tolerate wide fluctuations in thyroid hormone concentrations and survive without a thyroid gland. While benign thyroid tumours are common in older horses, other disorders like primary hypothyroidism or hyperthyroidism in adult horses and congenital hypothyroidism in foals are rare. There is a common misunderstanding regarding hypothyroidism in adult horses, especially when associated with the clinical profile of obesity, lethargy, and poor performance observed in dogs and humans. Low blood thyroid hormone concentrations are often detected in horses as a secondary response to metabolic and disease states, including with the nonthyroidal illness syndrome; however, it is important to note that low thyroid hormone concentrations in these cases do not necessarily indicate hypothyroidism. Assessing equine thyroid function involves measuring thyroid hormone concentrations, including total and free fractions of thyroxine (T4) and triiodothyronine (T3); however, interpreting these results can be challenging due to the pulsatile secretion of thyroid hormones and the many factors that can affect their concentrations. Dynamic testing, such as the thyrotropin-releasing hormone stimulation test, can help assess the thyroid gland response to stimulation. Although true hypothyroidism is extremely rare, thyroid hormone supplementation is commonly used in equine practice to help manage obesity and poor performance. This review focuses on thyroid gland pathophysiology in adult horses and foals, interpretation of blood thyroid hormone concentrations, and evaluation of horses with thyroid disorders. It also discusses the use of T4 supplementation in equine practice.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/37533378/