Equis ISSN 2398-2977

Endocrine: endogenous ACTH assay

Synonym(s): Endogenous adrenocorticotrophic hormone test

Contributor(s): Kathleen P Freeman, Han van der Kolk, David Rendle

Overview

  • Measures ACTH produced by pituitary gland; pars distalis and/or pars intermedia.
  • Elevated level in the majority of horses with pituitary pars intermedia dysfunction (PPID) Pituitary: adenoma due to production in pars intermedia.
  • Accepted as the test of choice for PPID.
  • Good correlation between ACTH concentration and pathology of the pars intermedia.
  • Production is affected by seasonal variation in pituitary activity with levels being higher in the Fall/Autumn. Seasonally-adjusted reference ranges should be used.
  • Concerns over the stability of ACTH following sampling have been overstated.

Sampling

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Tests

Methodologies

  • Radioimmunoassay.
  • Chemiluminescence.

Availability

  • Most veterinary commercial, reference and university laboratories.

Validity

Sensitivity

  • Varies between studies but around 70%.

Specificity

  • Varies between studies but around 60%.

Technique (intrinsic) limitations

  • Confounding effects of stress and other disease, including laminitis.
  • The stress of sampling in unhandled or needle-shy horses can have a confounding effect.
  • Some overlap of values with normal horses.
  • Check with laboratory to determine that their method has been validated for horses and that reference interval/guidelines for interpretation are available. Reference ranges vary between methods. Chemiluminescence is the method that is typically used in diagnostic laboratories.
  • Reference ranges have to be adjusted for season.

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Technician (extrinsic) limitations

  • Requires interpretation in conjunction with signalment and clinical signs.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Irvine K L, Burt K, Hill A J, Shaw S & Papasouliotis K (2016) Initial analytic quality assessment and method comparison of an immunoassay for adrenocorticotropic hormone measurement in equine samples. Vet Clin Pathol 45 (1), 154–163 PubMed.
  • Fouch√© N et al (2015) Venipuncture does not affect adrenocorticotropic hormone concentration in horses. Vet Rec 177 (9), 223–223 PubMed.
  • Rendle D I et al (2015) The effects of sample handling and N-phenylmaleimide on concentration of adrenocorticotrophic hormone in equine plasma. Equine Vet J 47 (5), 587-591 PubMed.
  • Diez de Castro E et al (2014) Influence of feeding status, time of the day, and season on baseline adrenocorticotropic hormone and the response to thyrotropin releasing hormone-stimulation test in healthy horses. Domest Anim Endocrinol 48, 77–83 PubMed.
  • Rendle D I, Litchfield E, Heller J & Hughes K J (2014) Investigation of rhythms of secretion and repeatability of plasma adrenocorticotropic hormone concentrations in healthy horses and horses with pituitary pars intermedia dysfunction. Equine Vet J 46 (1), 113–117 PubMed.
  • Rendle D I et al (2014) Investigation of single and paired measurements of adrenocorticotropic hormone for the diagnosis of pituitary pars intermedia dysfunction in horses. J Vet Intern Med 29 (1), 355–361 PubMed.
  • McGowan T, Pinchbeck G P & McGowan C M (2013) Evaluation of basal plasma α-melanocyte-stimulating hormone and adrenocorticotrophic hormone concentrations for the diagnosis of pituitary pars intermedia dysfunction from a population of aged horses. Equine Vet J 45 (1), 66–73 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.
  • 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.
  • Copas V E N & Durham A E (2011) Circannual variation in plasma adrenocorticotropic hormone concentrations in the UK in normal horses and ponies, and those with pituitary pars intermedia dysfunction. Equine Vet J 44 (4), 440–443 PubMed.
  • Cordero M, Shrauner B & McFarlane D (2011) Bioactivity of plasma ACTH from horses with PPID compared to normal horses. J Vet Intern Med 25, 664.
  • McFarlane D (2011) Equine pituitary pars intermedia dysfunction. Vet Clin of North Am Equine Pract 27 (1), 93–113 PubMed.
  • McFarlane D et al (2011) The effect of geographic location, breed, and pituitary dysfunction on seasonal adrenocorticotropin and α-melanocyte-stimulating hormone plasma concentrations in horses. J Vet Intern Med 25 (4), 872–881 PubMed.
  • Cravana C et al (2010) Effects of competitive and noncompetitive showjumping on total and free iodothyronines, β-endorphin, ACTH and cortisol levels of horses. Equine Vet J 38, 179–184 PubMed.
  • Lee Z-Y, Zylstra R & Haritou S J A (2010) The use of adrenocorticotrophic hormone as a potential biomarker of pituitary pars intermedia dysfunction in horses. Vet J 185 (1), 58–61 PubMed.
  • Fazio E, Medica P, Aronica V, Grasso L & Ferlazzo A (2008) Circulating β-endorphin, adrenocorticotrophic hormone and cortisol levels of stallions before and after short road transport: stress effect of different distances. Acta Vet Scand 50, 6 PubMed.
  • Fazio E, Medica P, Cravana C & Ferlazzo A (2008) Effects of competition experience and transportation on the adrenocortical and thyroid responses of horses. Vet Rec 163 (24), 713–716 PubMed.
  • Miller M A et al (2008) Correlation of pituitary histomorphometry with adrenocorticotrophic hormone response to domperidone administration in the diagnosis of equine pituitary pars intermedia dysfunction. Vet Pathol 45 (1), 26–38 PubMed.
  • Donaldson M T et al (2005) Variation in plasma adrenocorticotropic hormone concentration and dexamethasone suppression test results with season, age and sex in healthy ponies and horses. J Vet Intern Med 19, 217-222 PubMed.
  • Couetil L (1996) Plasma adrenocorticotropin concentration in healthy horses and in horses with clinical signs of hyperadrenocorticism. J Vet Intern Med 10 (1), 1-6 PubMed.
  • Van der Kolk J H et al (1995) Laboratory diagnosis of equine pituitary pars intermedia adenoma. Domestic Animal Endocrinol 12 (1), 35-39 PubMed.
  • Sojka J E et al (1995) Evaluation of endocrine function. Vet Clin North Am Equine Pract 11 (1), 415-435 PubMed.
  • Dybdal N O et al (1994) Diagnostic testing for pituitary pars intermedia dysfunction in horses. JAVMA 204, 627-632 PubMed.
  • Beech J et al (1987) Evaluation of thyroid, adrenal and pituitary function. Vet Clin North Am Equine Pract 3, 649-661 PubMed.


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