Merck Manual

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Professional Version

Hypocalcemic Disorders of Horses


Mark E. Peterson

, DVM, DACVIM-SAIM, Animal Endocrine Clinic, New York

Last review/revision Jul 2013 | Modified Oct 2022

Primary hypoparathyroidism is a rare but well documented disorder in horses. Affected horses have clinical signs consistent with hypocalcemia (ataxia, seizures, hyperexcitability, synchronous diaphragmatic flutter, tachycardia, tachypnea, muscle fasciculation, and ileus). As in other species, the diagnosis is based on the finding of low serum concentrations of calcium and PTH with high levels of phosphorus. As described above, treatment with intravenous and subsequently oral calcium combined with large doses of vitamin D should result in the remission of clinical signs associated with hypoparathyroidism.

Sepsis is one of the most common causes of hypocalcemia in horses admitted to veterinary hospitals. Total and ionized hypocalcemia are common in horses with severe GI disease and sepsis. Hypocalcemia with inappropriately low serum PTH concentrations also has been reported in foals. The underlying cause of hypocalcemia in foals remains to be determined. However, these foals may possibly have some form of hypoparathyroidism associated with sepsis.

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