Investigation of rhythms of secretion and repeatability of plasma adrenocorticotropic hormone concentrations in healthy horses and horses with pituitary pars intermedia dysfunction.
Abstract: There is little published information on whether measurement of plasma ACTH concentration at a single timepoint is a repeatable indicator of pituitary pars intermedia dysfunction (PPID). Objective: To determine whether ultradian or circadian fluctuations in ACTH production influence plasma ACTH concentration in normal horses and horses with PPID. Methods: Prospective observational study. Methods: Plasma ACTH concentration in 8 non-PPID horses and 8 horses with PPID was measured at 08.00, 11.00, 14.00 and 17.00 h on 5 nonconsecutive days within a 3 week period. In addition, at 08.30 h on one day, 6 samples were collected from each horse at precisely 5 min intervals over a period of 25 min. Descriptive and graphical analysis was performed and a linear mixed effects model was fitted to assess the effect of time of day on ACTH concentration in non-PPID and PPID horses. Results: Evidence of ultradian fluctuation in ACTH production was not identified in either non-PPID or PPID horses. Evidence for circadian fluctuation was identified in non-PPID horses; plasma ACTH concentrations were highest at 08.00 h and decreased through the day. There was no evidence of circadian fluctuation in PPID horses. In non-PPID horses, the magnitude of circadian changes in ACTH concentration was smaller than variations in concentration that occurred at random. Intrahorse variability of ACTH concentration was greater in PPID horses than in non-PPID horses. Conclusions: Ultradian and circadian fluctuations in ACTH concentration are unlikely to influence clinical decision making; however, variations of potential clinical relevance do occur in individual horses, for reasons that remain to be determined, and increase in magnitude with progression of PPID. Results of the current study indicate that when an ACTH concentration between 19 and 40 pg/ml is measured, further testing should be considered to increase the accuracy of PPID diagnosis.
© 2013 EVJ Ltd.
Publication Date: 2013-08-30 PubMed ID: 23742059DOI: 10.1111/evj.12114Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Adrenocorticotropic Hormone (ACTH)
- Circadian Rhythm
- Clinical Pathology
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Disease Progression
- Endocrine System
- Equine Health
- Health Monitoring
- Hormones
- Horses
- Metabolism
- Observational Study
- Pathophysiology
- Physiology
- Pituitary Pars Intermedia Dysfunction
- Plasma
- Veterinary Medicine
- Veterinary Practice
Summary
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This research article focuses on determining how adrenal cortical hormones (ACTH) fluctuate over time in horses, especially those diagnosed with pituitary pars intermedia dysfunction (PPID). Understanding these fluctuations helps to determine the most optimal times for diagnosing PPID in horses.
Objective and Methodology of the Study
- The main aim of the study was to establish whether there were any notable ultradian (occurring many times in a 24 hour period) or circadian (occurring in a routine daily rhythm) fluctuations in ACTH production in healthy horses and those suffering from PPID.
- The researchers conducted a prospective observational study on a sample of 8 non-PPID horses and 8 horses with PPID.
- The researchers measured plasma ACTH concentration in all horses at different times (08.00, 11.00, 14.00, and 17.00 hours) over five nonconsecutive days within a span of three weeks.
- The team also collected 6 additional samples from each horse, at 08:30 on one day, with precisely 5 minute intervals over a period of 25 minutes for thorough evaluation.
Results of the Study
- The study found no evidence of ultradian variations in ACTH production in either non-PPID or PPID horses.
- Circadian fluctuations were observed in non-PPID horses where the ACTH concentration was highest at 08.00 and decreased throughout the day. However, no such circadian rhythms were detected in horses diagnosed with PPID.
- Intrahorse variability of ACTH concentration was observed to be higher in PPID horses than in healthy horses, adding to the challenge of diagnosing this condition.
Conclusions
- The study concluded that fluctuations in ACTH concentration over time—whether circadian or ultradian—are unlikely to have a significant influence on clinical decision making when it comes to diagnosing PPID in horses.
- However, individual variations of potential clinical relevance do occur in horses, the precise reasons for which remain undetermined.
- The study also suggests that an ACTH concentration between 19 and 40 pg/ml warrants further testing to increase the accuracy of PPID diagnosis, especially given the inconsistency and variability within and among horses.
Cite This Article
APA
Rendle DI, Litchfield E, Heller J, Hughes KJ.
(2013).
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.
https://doi.org/10.1111/evj.12114 Publication
Researcher Affiliations
- School of Animal and Veterinary Sciences, Charles Sturt University, New South Wales, Australia.
MeSH Terms
- Adrenocorticotropic Hormone / blood
- Adrenocorticotropic Hormone / metabolism
- Animals
- Horse Diseases / blood
- Horse Diseases / metabolism
- Horses
- Pituitary Diseases / blood
- Pituitary Diseases / metabolism
- Pituitary Diseases / veterinary
- Pituitary Gland, Intermediate / pathology
Citations
This article has been cited 9 times.- Drozdzewska K, Gehlen H. Markers for internal neoplasia in the horse.. Vet Med Sci 2023 Jan;9(1):132-143.
- Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses.. Vet Sci 2022 Oct 10;9(10).
- Humphreys S, Kass PH, Magdesian KG, Goodrich E, Berryhill E. Seasonal variation of endogenous adrenocorticotropic hormone concentrations in healthy non-geriatric donkeys in Northern California.. Front Vet Sci 2022;9:981920.
- Thane K, Uricchio C, Frank N. Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses.. J Vet Intern Med 2022 Mar;36(2):770-777.
- Hicks GR, Fraser NS, Bertin FR. Changes Associated with the Peri-Ovulatory Period, Age and Pregnancy in ACTH, Cortisol, Glucose and Insulin Concentrations in Mares.. Animals (Basel) 2021 Mar 20;11(3).
- Hodge E, Kowalski A, Torcivia C, Lindborg S, Stefanovski D, Hart K, Frank N, van Eps A. Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol.. J Vet Intern Med 2019 Sep;33(5):2272-2279.
- Spelta CW. Equine pituitary pars intermedia dysfunction: current perspectives on diagnosis and management.. Vet Med (Auckl) 2015;6:293-300.
- Secombe CJ, Tan RHH, Perara DI, Byrne DP, Watts SP, Wearn JG. The Effect of Geographic Location on Circannual Adrenocorticotropic Hormone Plasma Concentrations in Horses in Australia.. J Vet Intern Med 2017 Sep;31(5):1533-1540.
- Rendle DI, Duz M, Beech J, Parkin T, Durham AE. Investigation of single and paired measurements of adrenocorticotropic hormone for the diagnosis of pituitary pars intermedia dysfunction in horses.. J Vet Intern Med 2015 Jan;29(1):355-61.
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