Discovered at UC Davis Equine Familial Isolated Hypoparathyroidism (EFIH)

Quick Summary

Equine familial isolated hypoparathyroidism (EFIH), previously termed idiopathic hypocalcemia, is an invariably fatal condition that causes involuntary contraction of muscles and seizures in Thoroughbred foals.
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hypocalcemia
thoroughbred
efih

Phenotype: Equine familial isolated hypoparathyroidism (EFIH) causes involuntary contraction of muscles and seizures in Thoroughbred foals and is invariably fatal. Blood work reveals low calcium, typically high phosphorus, and low or normal parathyroid hormone (PTH) concentrations, suggesting functional hypoparathyroidism.

Mode of Inheritance: Autosomal recessive

Alleles: N = normal, EFIH = equine familial isolated hypoparathyroidism variant

Breeds appropriate for testing: Thoroughbred

Explanation of results:

  • Horses with the N/N genotype do not have the genetic variant causing equine familial isolated hypoparathyroidism and cannot transmit the variant to any of their offspring.
  • Horses with the N/EFIH genotype carry one copy. They will have normal calcium levels and normal muscle control but can transmit the variant to 50% of their offspring, and if mated to another carrier, there is a 25% chance the foal will have EFIH.
  • Horses with the EFIH/EFIH genotype have two copies of the genetic variant causing equine familial isolated hypoparathyroidism and are likely to suffer from EFIH. This condition is fatal.
Price

$40 one test per animal

Additional Details

Equine familial isolated hypoparathyroidism (EFIH), previously termed idiopathic hypocalcemia, causes tetany (involuntary contraction of muscles) and seizures in Thoroughbred foals and is invariably fatal. Blood work reveals a low calcium, typically high phosphorus and low or normal parathyroid hormone (PTH) concentrations, suggesting functional hypoparathyroidism.

To date, EFIH has only been identified in the Thoroughbred breed and is inherited as an autosomal recessive trait. The genetic variant for EFIH was discovered in 2019, and genetic testing can now be performed to identify horses with the variant and avoid mating carriers that could produce affected foals.

The scientific study describing the identification of the genetic variant for EFIH is currently under peer-review for publication in a journal. When the manuscript is published, the VGL will update the educational content on our website and provide the reference.

Turnaround Time
5-10 business days
Type of Sample

Species

Breed

Type of Test

Results Reported As
Test Result Equine Familial Isolated Hypoparathyroidism

N/N

Normal. Horse does not have the EFIH variant.

N/EFIH

Horse is a carrier of the EFIH variant.

EFIH/EFIH

Affected. Horse has two copies of the EFIH variant. This is ultimately fatal.