The effect of starting time on dexamethasone suppression test results in horses.
Abstract: This study was conducted to investigate the effect of starting time on dexamethasone suppression test results in horses. Eight adult horses were used throughout the trial. Baseline cortisol levels were established by collecting cortisol levels twice daily, at 8:00 A.M. and 8:00 P.M. for 4 consecutive days. Morning baseline cortisol levels were 46.3 +/- 5.94 ng/ml, and evening baseline cortisol levels were 32.8 +/- 5.59 ng/ml. Although lower, the evening cortisol levels were not statistically different (P = 0.154) from the morning levels. Dexamethasone suppression tests initiated at either 9:00 A.M. or 9:00 P.M. were performed by collected a control blood sample, administering either 0.044 mg/kg dexamethasone or its vehicle intravenously and then collecting additional blood samples at 6, 12, 24, 36, and 48 hr after treatment. Mean cortisol levels at hr 0, 6, 12, 24, 36, and 48 after a dexamethasone injection given at 9:00 A.M. were 55.6 +/- 3.08, 6.4 +/- 2.05, 0.73 +/- 0.48, 11.0 +/- 5.82, 12.6 +/- 4.30, and 40.5 +/- 5.38 ng/ml respectively. Mean cortisol levels at hr 0, 6, 12, 24, 36, and 48 hr after a dexamethasone injection given at 9:00 P.M. were 45.0 +/- 6.03, 4.5 +/- 1.28, 0.20 +/- 0.12, 4.5 +/- 2.49, 23.4 +/- 5.88, and 29.5 +/- 6.61 ng/ml respectively. There was no statistical difference in cortisol values between A.M. and P.M. initiated tests at any hour post dexamethasone administration. There was no decrease in cortisol level after administration of dexamethasone vehicle.
Publication Date: 1993-01-01 PubMed ID: 8467642DOI: 10.1016/0739-7240(93)90002-sGoogle Scholar: Lookup
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- Journal Article
Summary
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The research article discusses a study of the influence of different starting times (morning or evening) on the outcomes of dexamethasone suppression tests in horses.
Introduction
The aim of the study was to ascertain if the time of day a dexamethasone suppression test (used to diagnose disorders of the endocrine system in animals) is initiated can impact the results. Eight adult horses were used in this trial.
Experiment Design
- To determine baseline cortisol levels, cortisol was measured twice daily (at 8:00 A.M. and 8:00 P.M.) for 4 consecutive days. The average morning cortisol levels were found to be 46.3 ng/ml and the evening levels were 32.8 ng/ml. Although the evening levels were lower, the difference was not statistically significant.
- The dexamethasone suppression tests were carried out by first collecting a control blood sample, followed by administering either the drug dexamethasone or a vehicle (a substance that has no therapeutic effect used as a medium to deliver a drug) intravenously. Subsequent blood samples were then collected at 6, 12, 24, 36, and 48 hours after treatment. This test was performed twice, once at 9:00 A.M and again at 9:00 P.M.
Results and Analysis
- The mean cortisol levels at various hours post-injection when the dexamethasone was given at 9:00 A.M. were noted, as well as when it was given at 9:00 P.M.
- When comparing these cortisol values, there was no affirmative statistical difference between tests started in the morning and those initiated in the evening.
- It was also noted that there was no decrease in cortisol levels post the administration of the dexamethasone vehicle, validating that the observed decrease in cortisol levels was due to the administration of dexamethasone and not the vehicle itself.
Conclusion
The study concludes that the timing of the administration of the dexamethasone suppression test, whether in the morning or evening, does not significantly affect the results of the test. This could imply that the test can be performed at any time of the day, reducing scheduling constraints and increasing convenience for veterinary diagnostics.
Cite This Article
APA
Sojka JE, Johnson MA, Bottoms GD.
(1993).
The effect of starting time on dexamethasone suppression test results in horses.
Domest Anim Endocrinol, 10(1), 1-5.
https://doi.org/10.1016/0739-7240(93)90002-s Publication
Researcher Affiliations
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana 47907.
MeSH Terms
- Analysis of Variance
- Animals
- Circadian Rhythm
- Dexamethasone
- Female
- Horses / blood
- Horses / physiology
- Hydrocortisone / blood
- Male
- Pituitary-Adrenal System / physiology
- Radioimmunoassay
- Reference Values
- Sensitivity and Specificity
- Time Factors
Citations
This article has been cited 1 times.- Held F, Ekstrand C, Cvijovic M, Gabrielsson J, Jirstrand M. Modelling of oscillatory cortisol response in horses using a Bayesian population approach for evaluation of dexamethasone suppression test protocols.. J Pharmacokinet Pharmacodyn 2019 Feb;46(1):75-87.
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