Effects of withholding feed on thyrotropin-releasing hormone stimulation test results and effects of combined testing on oral sugar test and thyrotropin-releasing hormone stimulation test results in horses.
Abstract: OBJECTIVE To assess effects of withholding feed on thyrotropin-releasing hormone (TRH) stimulation test results used in diagnosis of pituitary pars intermedia dysfunction in horses and determine effects of combined testing on results of the TRH stimulation test and the oral sugar test (OST) used in diagnosis of equine metabolic syndrome. ANIMALS 30 adult horses. PROCEDURES All horses underwent TRH stimulation tests under fed and nonfed conditions, an OST alone, and an OST combined with TRH stimulation testing. For TRH stimulation tests, plasma ACTH concentrations were measured before (baseline) and 10 minutes after (poststimulation) IV TRH administration. For the OST, plasma glucose and insulin concentrations were measured before (baseline) and 60 and 90 minutes after oral corn syrup administration. For combined testing, the TRH stimulation test was initiated immediately after 60-minute posttreatment sample collection for the OST. Results were compared among methods by Wilcoxon matched-pairs, signed rank tests, paired t tests, and Bland-Altman analysis. RESULTS Feeding conditions did not affect median ACTH concentrations when TRH stimulation tests were performed alone. Median baseline ACTH concentration did not differ between TRH stimulation tests performed alone (under fed or nonfed conditions) and those combined with OSTs. Median poststimulation ACTH concentration was significantly lower for combined tests than for solitary TRH stimulation tests. Mean 60-minute plasma glucose concentration was significantly lower for solitary OSTs than for combined tests, but this difference could not be attributed to TRH administration. CONCLUSIONS AND CLINICAL RELEVANCE Combined testing in the manner described impacted ACTH concentrations during TRH stimulation tests and is not recommended at this time.
Publication Date: 2016-06-28 PubMed ID: 27347827DOI: 10.2460/ajvr.77.7.738Google Scholar: Lookup
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- Clinical Trial
- Journal Article
- Adrenocorticotropic Hormone (ACTH)
- Adult Horses
- Blood
- Clinical Study
- Comparative Study
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Equine Diseases
- Equine Health
- Equine Metabolic Syndrome
- Feeding Practices
- Glucose
- Hormones
- Insulin
- Metabolism
- Physiology
- Pituitary Pars Intermedia Dysfunction
- Thyroid Hormones
- Veterinary Medicine
- Veterinary Research
Summary
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The research article investigates how feeding conditions and combined testing affect the results of two diagnostic tests used in horses: the thyrotropin-releasing hormone (TRH) stimulation test for pituitary pars intermedia dysfunction and the oral sugar test (OST) for equine metabolic syndrome. It concludes that combined testing affects ACTH levels in TRH stimulation tests and is not currently recommended.
Methodology
- The study was conducted on 30 adult horses. The tests carried out included TRH stimulation tests under fed and non-fed conditions, an OST on its own, and an OST combined with TRH stimulation testing.
- In the TRH stimulation tests, plasma ACTH levels were measured before (baseline) and 10 minutes after (post stimulation) intravenous TRH administration. This test is important for diagnosing pituitary pars intermedia dysfunction in horses, a common hormonal disorder.
- During the OST, plasma glucose and insulin concentrations were measured before (baseline) and 60 and 90 minutes following oral corn syrup administration. This test is used to diagnose equine metabolic syndrome, a condition similar to type 2 diabetes in humans.
- The combined testing involved initiating the TRH stimulation test right after the OST’s 60-minute post-treatment sampling. The intention was to examine how simultaneous testing affects the results of these two diagnostic tests.
Results
- The results showed that the feeding conditions, whether the horses were fed or not, did not affect median ACTH concentrations when TRH stimulation tests were performed alone.
- The median baseline ACTH level showed no difference between the standalone TRH stimulation tests (whether under fed or non-fed conditions) and those combined with the OST.
- However, when the tests were combined, the median post-stimulation ACTH concentration was considerably lower than in standalone TRH stimulation tests.
- Similarly, the mean 60-minute plasma glucose concentration was significantly lower for solitary OSTs than when combined with TRH tests. But the discrepancy was not related to TRH administration.
Conclusions
- The study’s findings suggest that combined testing impacts ACTH concentrations during TRH stimulation tests and should not be used at this time.
- This may imply that the simultaneous performance of OSTs and TRH stimulation tests may compromise the accurate diagnosis of pituitary pars intermedia dysfunction or equine metabolic syndrome in horses.
- Further research may be necessary to refine combined testing procedures or to understand fully how simultaneous testing affects the results of these diagnostic tests.
Cite This Article
APA
Restifo MM, Frank N, Hermida P, Sanchez-Londoño A.
(2016).
Effects of withholding feed on thyrotropin-releasing hormone stimulation test results and effects of combined testing on oral sugar test and thyrotropin-releasing hormone stimulation test results in horses.
Am J Vet Res, 77(7), 738-748.
https://doi.org/10.2460/ajvr.77.7.738 Publication
Researcher Affiliations
MeSH Terms
- Adrenocorticotropic Hormone / blood
- Animal Feed
- Animals
- Fasting
- Horses
- Pituitary Gland, Intermediate / physiopathology
- Thyrotropin-Releasing Hormone / metabolism
Citations
This article has been cited 8 times.- Stefanovski D, Robinson MA, Van Eps A. Effect of a GLP-1 mimetic on the insulin response to oral sugar testing in horses. BMC Vet Res 2022 Jul 29;18(1):294.
- 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.
- Kam YN, McKenzie K, Coyle M, Bertin FR. Repeatability of a thyrotropin-releasing hormone stimulation test for diagnosis of pituitary pars intermedia dysfunction in mature horses. J Vet Intern Med 2021 Nov;35(6):2885-2890.
- Gehlen H, Schwarz B, Bartmann C, Gernhardt J, Stöckle SD. Pituitary Pars Intermedia Dysfunction and Metabolic Syndrome in Donkeys. Animals (Basel) 2020 Dec 8;10(12).
- 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.
- Durham AE, Frank N, McGowan CM, Menzies-Gow NJ, Roelfsema E, Vervuert I, Feige K, Fey K. ECEIM consensus statement on equine metabolic syndrome. J Vet Intern Med 2019 Mar;33(2):335-349.
- Menzies-Gow NJ. Equine Pituitary Pars Intermedia Dysfunction. Vet Sci 2025 Aug 20;12(8).
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