Equis ISSN 2398-2977

Endocrine: parathyroid hormone assay

Synonym(s): PTH assay

Contributor(s): Kathleen P Freeman, Ramiro Toribio, Han van der Kolk


  • There are several assays to measure equine parathyroid hormone (PTH) concentrations in serum or plasma.
  • These assays determine either fragments of PTH or intact PTH (i-PTH).
  • The assays are valuable to assess primary or secondary alterations of parathyroid gland function that can result in an abnormal mineral metabolism.


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  • Rat and human PTH immunoradiometric (IRMA) assays can be used to detect equine intact PTH (i-PTH).
  • Human immunochemiluminometric assays (ICMA) have been used to detect equine i-PTH.
  • New human IRMA to detect whole PTH (w-PTH) can also be used in horses.


  • Limited; only available in a few veterinary commercial/reference/university laboratories.
  • May be available via human hospitals.
  • Preference must be given to intact PTH assays, rather than to C-terminal or N-terminal PTH assays which do not detect the intact peptide.



  • Check with laboratory to determine that their method has been validated for horses and that reference interval/guidelines for interpretation are available.

Result Data

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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Estepa J C et al (2003) Validation and clinical utility of a novel immunoradiometric assay exclusively for biologically active whole parathyroid hormone in the horse. Equine Vet J 35 (3), 291-295 PubMed.
  • Toribio R E et al (2001)Comparison of serum parathyroid hormone and ionized calcium and magnesium concentrations and fractional urinary clearance of calcium and phosphorus in healthy horses and horses with enterocolitis. Am J Vet Res 62 (6), 938-947 PubMed.
  • Estepa J C et al (1998) Measurement of parathyroid hormone in horses. Equine Vet J 30 (6), 476-481 PubMed.
  • Van der Kolk J H, Geelen S N, Jonker F H, Pycock J F & Koeman J P (1998) Hypertrophic osteopathy associated with ovarian carcinoma in a mare. Vet Rec 143 (6), 172-173 PubMed.
  • Cooper S R et al (1995) Effects of dietary cation-anion balance on blood pH, acid-base parameters, serum and urine mineral levels and parathyroid hormone (PTH) in weaning horses. J Equine Vet Sci 15 (10), 417-420.
  • Elfers R S, Bayly W M et al (1985) Alterations in calcium, phosphorus and C-terminal parathyroid hormone levels in equine acute renal disease. Cornell Vet 76 (3), 317-329 PubMed.
  • Brobst D F, Bayly W M et al (1982) Parathyroid hormone evaluation in normal horses and horses with renal failure. J Equine Vet Sci (5), 150-157.

Other sources of information

  • Toribio R E (2004) Calcium Disorders. In: Equine Internal Medicine. Eds: Reed S M, Bayly W M & Sellon D C. 2nd edn. Saunders, USA. pp 1295-1327.
  • Fenger C K (1998) Disorders of Calcium Metabolism. In: Equine Internal Medicine. Eds: Reed S M & Bayly W M. Philadelphia: W B Saunders Co. pp 925-934.