Diagnosis and treatment of confirmed and suspected primary hyperparathyroidism in equids: 17 cases (1999-2016).
Authors: Gorenberg E B, Johnson A L, Magdesian K G, Bertin F-R, Costa L R R, Theelen M J P, Durward-Akhurst S A, Cruz Villagrán C, Carslake H, Frank N, Tomlinson J E
Journal: Equine veterinary journal
Summary
Primary hyperparathyroidism remains a rare diagnosis in horses and mules, yet when it does occur, recognising the condition and selecting appropriate treatment significantly impacts outcomes. This retrospective analysis of 17 cases collated from university records and veterinary networks identified hypercalcaemia (in 10 cases) and progressive weight loss (in 12 cases) as the most frequent presenting signs, with confirmation requiring elevated parathyroid hormone levels or histopathological evidence of parathyroid adenoma. Ultrasonography and technetium-99m sestamibi scintigraphy proved effective localisation tools, successfully identifying suspected tumours in 12 of 14 imaged equids; notably, adenomas situated at the thoracic inlet were the most amenable to surgical cure, with five of six cases achieving complete resolution of hypercalcaemia following excision. Conversely, tumours within thyroid tissue or those in other locations often persisted despite surgical intervention, and medical management alone failed to resolve the condition in all four treated cases. For practitioners encountering a hypercalcaemic equid with elevated PTH and normal renal function, combining ultrasonography with scintigraphy to localise disease at the thoracic inlet may optimise surgical success rates, though the rarity of this condition and modest case numbers mean further evidence is needed to guide treatment decisions for atypical presentations.
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Practical Takeaways
- •Suspect primary hyperparathyroidism in horses presenting with progressive weight loss and persistent hypercalcemia with elevated PTH levels; diagnosis requires imaging with ultrasonography or scintigraphy
- •Surgical excision of parathyroid adenomas located at the thoracic inlet offers the best chance of complete resolution, whereas tumours in other locations and medical management have lower success rates
- •Combination imaging with both ultrasonography and scintigraphy improves localisation of parathyroid tumours compared to either modality alone (9/10 cases successfully localised with both)
Key Findings
- •Weight loss (12/17) and hypercalcemia (10/17) were the most common presenting complaints in equids with primary hyperparathyroidism
- •PTH was elevated above reference range in 12/17 cases, and parathyroid tumours were successfully localised in 12/14 equids using ultrasonography and/or technetium 99m sestamibi scintigraphy
- •Surgical excision achieved complete cure in 5 of 6 cases where tumours at the thoracic inlet were successfully removed, but remained unsuccessful in other locations
- •Four surgically explored cases, four medically treated cases, and three untreated cases all remained hypercalcemic despite intervention attempts