Primary Hypoparathyroidism and Recurring Hypocalcemia in a Quarter Horse Gelding-A Case Report.
Authors: Thompson Alexis C, Mochal-King Cathleen
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Primary Hypoparathyroidism in an Equine Patient Whilst hypoparathyroidism remains exceptionally rare in horses, this 2021 case report documents a 17-year-old Quarter Horse gelding presenting with severe hypocalcaemia secondary to parathyroid hormone insufficiency—a condition that warrants awareness among practitioners managing horses with unexplained neuromuscular signs. The gelding presented with generalised muscle fasciculations, synchronous diaphragmatic flutter, and hypermetric hindlimb gait alongside marked biochemical abnormalities: severe hypocalcaemia, hyperphosphatemia, hypokalemia, and hypomagnesemia. Initial intravenous and oral calcium supplementation resolved clinical signs within 36 hours, but symptoms recurred following treatment discontinuation, prompting diagnosis of primary hypoparathyroidism based on low parathyroid hormone concentrations despite low ionised calcium. Long-term management with feed-grade calcium carbonate and fat-soluble vitamin supplementation (vitamins A, D, and E) proved successful, maintaining clinical stability without apparent performance decline. This case emphasises that whilst uncommon, hypoparathyroidism should feature in the differential diagnosis of horses presenting with acute-onset tremors and neuromuscular signs accompanied by severe hypocalcaemia, and that oral calcium supplementation—even at modest cost using feed-grade lime—may provide a sustainable management strategy when underlying endocrine dysfunction prevents spontaneous resolution.
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Practical Takeaways
- •Hypoparathyroidism is rare in horses but should be considered in cases of unexplained severe hypocalcemia with muscle tremors, fasciculations, or diaphragmatic flutter; confirm diagnosis with low PTH in presence of low ionized calcium
- •Acute hypocalcemia responds rapidly to IV calcium therapy, but affected horses require long-term oral supplementation with calcium carbonate to prevent recurrence
- •Feed-grade lime (calcium carbonate) is an effective and practical long-term supplementation strategy that does not compromise performance in treated horses
Key Findings
- •A 17-year-old Quarter Horse gelding presented with severe hypocalcemia (low ionized calcium with low parathyroid hormone) manifesting as muscle tremors, fasciculations, and synchronous diaphragmatic flutter
- •Initial intravenous and oral calcium supplementation resolved clinical signs within 36 hours but signs recurred upon treatment discontinuation
- •Long-term oral calcium carbonate (feed-grade lime) and vitamin AED supplementation successfully maintained normal calcium levels and prevented disease recurrence without affecting performance