Equis ISSN 2398-2977

Endocrine: cortisol assay

Contributor(s): Annalisa Barrelet, Kathleen P Freeman, Han van der Kolk, Ramiro Toribio, David Rendle


  • Cortisol is quantitatively the most important adrenal cortical steroid found in the blood.
  • It is synthesized in the adrenal cortex under the influence of ACTH secreted from the anterior pituitary gland, which in turn is regulated by corticotrophin releasing factor (CRF) from the hypothalamus.
  • Negative feedback by cortisol regulates CRH and ACTH release. Various factors influence CRH production, including stress of fear, pain, injury and/or pyrexia.
  • A diurnal rhythm also operates with low levels of cortisol in the afternoon/evening and higher levels in the morning.


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  • Chemilluminesence.
  • Radio immunoassay (RIA).


  • Widely available in referral laboratories.

Result Data

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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hart K A et al (2016) Effect of age, season, body condition, and endocrine status on serum free cortisol fraction and insulin concentration in horses. J Vet Intern Med 30 (2), 653–663 PubMed.
  • Monk C S (2014) Detection of endogenous cortisol in equine tears and blood at rest and after simulated stress. Vet Ophthal 17 Suppl 1, 53–60 PubMed.
  • Bohák Z et al (2013) Monitoring the circadian rhythm of serum and salivary cortisol concentrations in the horse. Domest Anim Endocrinol 45 (1), 38–42 PubMed.
  • Stewart A J et al (2013) Validation of a low-dose adrenocorticotropic hormone stimulation test in healthy neonatal foals. JAVMA 243 (3), 399–405 PubMed.
  • Cordero M, Brorsen B W & McFarlane D (2012) Circadian and circannual rhythms of cortisol, ACTH, and α-melanocyte-stimulating hormone in healthy horses. Domest Anim Endocrinol 43 (4), 317–324 PubMed.
  • Gold J R, Cohen N D & Welsh T H Jr (2012) Association of adrenocorticotrophin and cortisol concentrations with peripheral blood leukocyte cytokine gene expression in septic and nonseptic neonatal foals. J Vet Intern Med 26 (3), 654–661 PubMed.
  • Ayala I et al (2012) Cortisol, adrenocorticotropic hormone, serotonin, adrenaline and noradrenaline serum concentrations in relation to disease and stress in the horse. Res Vet Sci 93 (1), 103–107 PubMed.
  • Hart K A (2012) The use of cortisol for the objective assessment of stress in animals: Pros and cons. Vet J 192 (2), 137–139 PubMed.
  • Hart K A et al (2012) Daily endogenous cortisol production and hydrocortisone pharmacokinetics in adult horses and neonatal foals. Am J Vet Res 73 (1), 68–75 PubMed.
  • Hart K A & Barton M H (2011) Adrenocortical insufficiency in horses and foals. Vet Clin of North Am: Equine Pract 27 (1), 19–34 PubMed.
  • Hart K A et al (2011) Serum free cortisol fraction in healthy and septic neonatal foals. J Vet Intern Med 25 (2), 345–355 PubMed.
  • Wong D M et al (2009) Baseline plasma cortisol and ACTH concentrations and response to low-dose ACTH stimulation testing in ill foals. JAVMA 234 (1), 126–132 PubMed.
  • Van der Kolk J H et al (2001) Salivary and plasma concentration of cortisol in normal horses and horses with Cushing's disease. Equine Vet J 33 (2), 211-213 PubMed.