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Adrenocorticotropin concentration following administration of thyrotropin-releasing hormone in healthy horses and those with pituitary pars intermedia dysfunction and pituitary gland hyperplasia.
Abstract: To compare the effect of thyrotropin-releasing hormone (TRH) administration on endogenous ACTH concentrations in healthy horses and those with pituitary pars inter-media hyperplasia and compare the test with the dexamethasone suppression test (DST). Methods: Prospective case series. Methods: 15 horses with clinical signs of pituitary pars intermedia dysfunction (PPID), 4 horses with equivocal signs of PPID, and 29 horses without signs of PPID. Methods: ACTH concentrations prior to and after administration of TRH were measured 61 times in 48 horses. Results of the DST (cortisol response) were compared with those of the TRH test in 29 horses. Thirty-three horses (24 with no clinical signs of PPID, 5 with clinical signs of PPID, and 4 with equivocal clinical signs of PPID) were euthanized and necropsied and their pituitary glands evaluated. Results: ACTH concentrations increased in all horses, but magnitude and duration of increase were significantly higher in horses with PPID. Endogenous ACTH concentrations were influenced by season. The ACTH baseline concentrations and response to TRH were not correlated with results of the DST. Results of DST were abnormal only in clinically abnormal horses or those with pars intermedia hyperplasia, but were within reference range in 17 of 26 tests in these horses. Conclusions: The ACTH response to TRH is a useful test for diagnosis of pituitary gland hyperplasia, particularly in horses in which baseline ACTH concentrations are within reference range. The DST was specific but not sensitive and was inconsistent for individuals, and results often did not agree with the TRH test response.
Publication Date: 2007-08-03 PubMed ID: 17669045DOI: 10.2460/javma.231.3.417Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Adrenocorticotropic Hormone (ACTH)
- Case Reports
- Clinical Pathology
- Clinical Study
- Comparative Study
- Cortisol
- Dexamethasone
- Diagnostic Technique
- Disease Diagnosis
- Endocrine System
- Epidemiology
- Equine Health
- Hormones
- Horses
- Necropsy
- Pituitary
- Pituitary Pars Intermedia Dysfunction
- Thyrotropin-Releasing Hormone
- Veterinary Research
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research investigated the effect of thyrotropin-releasing hormone (TRH) on adrenocorticotropin (ACTH) concentrations in horses, specifically comparing healthy horses and those with pituitary conditions. The researchers used this comparison to evaluate the effectiveness of the TRH test as a diagnostic tool for pituitary disorders.
Methodology
- The researchers used a prospective case series involving a number of horses in different health conditions: 15 horses exhibiting signs of pituitary pars intermedia dysfunction (PPID), 4 with equivocal symptoms of PPID, and 29 healthy horses showing no signs of PPID.
- They measured ACTH concentrations before and after the administration of TRH a total of 61 times in 48 horses.
- They then compared the results of the TRH test, which measures ACTH response, to the dexamethasone suppression test (DST), which measures cortisol response, in 29 of the horses.
- Additionally, 33 horses (including healthy ones and those with PPID symptoms) were euthanized and their pituitary glands were examined post-mortem.
Results
- ACTH concentrations increased in all horses after the administration of TRH. However, the degree and duration of the increase were significantly higher in horses with PPID.
- They found that the ACTH baseline concentrations and the response to TRH administration did not correlate with the results of the DST.
- The researchers also observed that endogenous ACTH concentrations varied by season.
- While results of DST were abnormal only in clinically abnormal horses or those with pars intermedia hyperplasia, the test produced results within the reference range in 17 of 26 corresponding examinations.
Conclusions
- The researchers concluded that the ACTH response to TRH administration is a useful diagnostic tool for identifying pituitary gland hyperplasia, particularly in horses with baseline ACTH concentrations within the reference range.
- Conversely, the DST, which measures cortisol response, only showed good specificity but poor sensitivity and inconsistent results. Therefore, it did not often align with the results of the TRH test.
Cite This Article
APA
Beech J, Boston R, Lindborg S, Russell GE.
(2007).
Adrenocorticotropin concentration following administration of thyrotropin-releasing hormone in healthy horses and those with pituitary pars intermedia dysfunction and pituitary gland hyperplasia.
J Am Vet Med Assoc, 231(3), 417-426.
https://doi.org/10.2460/javma.231.3.417 Publication
Researcher Affiliations
- Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, USA.
MeSH Terms
- Adrenocorticotropic Hormone / blood
- Animals
- Dexamethasone / pharmacology
- Diagnosis, Differential
- Female
- Hormones / pharmacology
- Horse Diseases / blood
- Horse Diseases / diagnosis
- Horses
- Hydrocortisone / blood
- Hyperplasia / blood
- Hyperplasia / diagnosis
- Hyperplasia / veterinary
- Male
- Pituitary Diseases / blood
- Pituitary Diseases / diagnosis
- Pituitary Diseases / veterinary
- Pituitary Gland, Intermediate / physiopathology
- Pituitary Neoplasms / blood
- Pituitary Neoplasms / diagnosis
- Pituitary Neoplasms / veterinary
- Prospective Studies
- Sensitivity and Specificity
- Thyrotropin-Releasing Hormone / pharmacology
Citations
This article has been cited 16 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. Prospective Case Series of Clinical Signs and Adrenocorticotrophin (ACTH) Concentrations in Seven Horses Transitioning to Pituitary Pars Intermedia Dysfunction (PPID). Vet Sci 2022 Oct 17;9(10).
- Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses. Vet Sci 2022 Oct 10;9(10).
- Hinrichsen SL, Yuen KY, Dryburgh EL, Bertin FR, Stewart AJ. Short-Term Effects of Temperature and Thyrotropin-Releasing Hormone Stimulation on Adrenocorticotropin Stability in Horses. Animals (Basel) 2022 Jan 28;12(3).
- Nitzsche AM, Fey K, Büttner K, Gröf M, Staszyk C. The Gingiva of Horses With Pituitary Pars Intermedia Dysfunction: A Macroscopic Anatomical Evaluation. Front Vet Sci 2021;8:786971.
- 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.
- Tatum RC, McGowan CM, Dean RS, Ireland JL. Equine pituitary pars intermedia dysfunction: Identifying research priorities for diagnosis, treatment and prognosis through a priority setting partnership. PLoS One 2021;16(1):e0244784.
- Horn R, Stewart AJ, Jackson KV, Dryburgh EL, Medina-Torres CE, Bertin FR. Clinical implications of using adrenocorticotropic hormone diagnostic cutoffs or reference intervals to diagnose pituitary pars intermedia dysfunction in mature horses. J Vet Intern Med 2021 Jan;35(1):560-570.
- Gehlen H, Jaburg N, Merle R, Winter J. Can Endocrine Dysfunction Be Reliably Tested in Aged Horses That Are Experiencing Pain?. Animals (Basel) 2020 Aug 14;10(8).
- Hu K, Stewart AJ, Yuen KY, Hinrichsen S, Dryburgh EL, Bertin FR. The effect of freeze-thaw cycles on determination of immunoreactive plasma adrenocorticotrophic hormone concentrations in horses. J Vet Intern Med 2020 May;34(3):1350-1356.
- Horn R, Bertin FR. Evaluation of combined testing to simultaneously diagnose pituitary pars intermedia dysfunction and insulin dysregulation in horses. J Vet Intern Med 2019 Sep;33(5):2249-2256.
- 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.
- Banse HE, Schultz N, McCue M, Geor R, McFarlane D. Comparison of two methods for measurement of equine adrenocorticotropin. J Vet Diagn Invest 2018 Mar;30(2):233-237.
- 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.
- Hart KA, Wochele DM, Norton NA, McFarlane D, Wooldridge AA, Frank N. Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses. J Vet Intern Med 2016 Mar-Apr;30(2):653-63.
- 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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