Results of a combined dexamethasone suppression/thyrotropin-releasing hormone stimulation test in healthy horses and horses suspected to have a pars intermedia pituitary adenoma.
Abstract: To evaluate results of a combined dexamethasone suppression/thyrotropin-releasing hormone (TRH) stimulation test in horses suspected clinically to have a pars intermedia pituitary adenoma (PIPA). Methods: Case-control study. Methods: 7 healthy adult horses and 5 horses suspected to have a PIPA. Methods: A baseline blood sample was collected, and dexamethasone (40 micrograms/kg [18 micrograms/lb] of body weight, IV) was administered; a second blood sample was collected 3 hours later, and TRH (1.1 mg, IV) was administered; serial blood samples were collected 15, 30, 45, 60, and 90 minutes and 21 hours after TRH administration (24 hours after dexamethasone injection). Cortisol concentration was determined for all blood samples. Results: Baseline cortisol concentration was significantly lower in horses suspected to have a PIPA than in healthy horses. Cortisol concentration was suppressed by dexamethasone in both groups; however, after TRH administration, cortisol concentration returned to baseline values in horses suspected to have a PIPA, but not in healthy horses. Concentration was still less than the baseline value 24 hours after dexamethasone administration in healthy horses. Conclusions: The combined dexamethasone suppression/TRH stimulation test may be a useful diagnostic test in horses suspected to have a PIPA. For clinical application, collection of a blood sample 30 minutes after TRH administration is recommended.
Publication Date: 1997-07-01 PubMed ID: 9215417
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Blood Analysis
- Case Reports
- Case-Control Study
- Clinical Findings
- Clinical Pathology
- Clinical Study
- Comparative Study
- Cortisol
- Dexamethasone
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Endocrine System
- Equine Health
- Hormones
- Horses
- Pituitary Pars Intermedia Dysfunction
- Thyrotropin-Releasing Hormone
- Veterinary Care
- Veterinary Medicine
- Veterinary Research
Summary
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The research evaluates the combined use of dexamethasone and thyrotropin-releasing hormone (TRH) in diagnosing a certain type of pituitary gland tumor called pars intermedia pituitary adenoma (PIPA) in horses.
Introduction
Pars intermedia pituitary adenoma (PIPA) is a type of pituitary gland tumor. In this study, the researchers used a combined test of dexamethasone suppression and thyrotropin-releasing hormone (TRH) stimulation to identify the presence of PIPA in horses.
Method
- The study was a case-control type, involving seven healthy adult horses and five horses suspected to have PIPA.
- A baseline blood sample was collected from each horse.
- Subsequently, each horse was given an intravenous (IV) injection of dexamethasone at a dose of 40 micrograms/kg of body weight.
- A second blood sample was collected three hours after the dexamethasone injection. After this, TRH was administered intravenously at a dose of 1.1 mg.
- After the TRH injection, blood samples were collected at 15, 30, 45, 60, and 90 minute intervals, and then 21 hours later, which marked 24 hours after the initial dexamethasone injection.
- The cortisol concentration in each blood sample was determined as cortisol levels can indicate the presence of PIPA.
Results
- At baseline, the cortisol concentration was found to be significantly lower in horses suspected of having PIPA than in healthy horses.
- The dexamethasone suppressed cortisol concentration in both groups of horses.
- However, following the administration of TRH, cortisol levels returned to baseline values in horses suspected of having PIPA, but not in healthy horses. This suggests a distinct reaction in horses with PIPA compared to healthy horses.
- In healthy horses, the cortisol concentration was still lower than the baseline value even 24 hours after the dexamethasone injection.
Conclusion
Based on the results of this study, the combined test of dexamethasone suppression and TRH stimulation could be a reliable diagnostic procedure for horses suspected to have PIPA. The research recommends that a blood sample be collected for cortisol level determination 30 minutes after TRH administration when this test is applied in a clinical setting.
Cite This Article
APA
Eiler H, Oliver JW, Andrews FM, Fecteau KA, Green EM, McCracken M.
(1997).
Results of a combined dexamethasone suppression/thyrotropin-releasing hormone stimulation test in healthy horses and horses suspected to have a pars intermedia pituitary adenoma.
J Am Vet Med Assoc, 211(1), 79-81.
Publication
Researcher Affiliations
- Department of Animal Science, College of Veterinary Medicine, University of Tennessee, Knoxville 37996-4500, USA.
MeSH Terms
- Adenoma / diagnosis
- Adenoma / physiopathology
- Adenoma / veterinary
- Animals
- Case-Control Studies
- Dexamethasone
- Female
- Glucocorticoids
- Horse Diseases / diagnosis
- Horse Diseases / physiopathology
- Horses / physiology
- Hydrocortisone / blood
- Pituitary Gland / physiopathology
- Pituitary Neoplasms / diagnosis
- Pituitary Neoplasms / physiopathology
- Pituitary Neoplasms / veterinary
- Receptors, Thyrotropin-Releasing Hormone / antagonists & inhibitors
- Receptors, Thyrotropin-Releasing Hormone / drug effects
- Thyrotropin-Releasing Hormone
Citations
This article has been cited 1 times.- 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).
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