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

Self Cite

183

227

Equine metabolic syndrome (EMS) is a widely recognized collection of risk factors for endocrinopathic laminitis. The most important of these risk factors is insulin dysregulation (ID). Clinicians and horse owners must recognize the presence of these risk factors so that they can be targeted and controlled to reduce the risk of laminitis attacks. Diagnosis of EMS is based partly on the horse's history and clinical examination findings, and partly on laboratory testing. Several choices of test exist which examine different facets of ID and other related metabolic disturbances. EMS is controlled mainly by dietary strategies and exercise programs that aim to improve insulin regulation and decrease obesity where present. In some cases, pharmacologic aids might be useful. Management of an EMS case is a long‐term strategy requiring diligence and discipline by the horse's carer and support and guidance from their veterinarians.

Section: Laboratory Diagnosismentioning

confidence: 99%

ECEIM consensus statement on equine metabolic syndrome

Durham¹,

Frank

McGowan

et al. 2019

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183

227

“…Each OST was classified as positive or negative (OST outcome) based on current accepted cutoffs for ID in horses . A fasting baseline insulin concentration ≥ 20 μIU/mL or insulin concentration at 60 or 90 minutes after oral sugar ≥45 μIU/mL was considered a positive outcome for the OST when measurement of insulin alone was used.…”

Section: Methodsmentioning

confidence: 99%

“…It is often clinically indicated to test for both PPID and ID in the same animal, making a protocol that temporally combines an OST with a TRH stimulation test highly desirable for efficient clinical testing in animals with suspect PPID or ID or both, particularly in a field setting. Unfortunately, performing an OST before a TRH stimulation test blunts ACTH results after stimulation, resulting in false‐negative PPID tests, precluding the use of a combined protocol with this order of testing . The reverse order of testing has not yet been evaluated, and the aim of this study was to evaluate the effects of a TRH stimulation test on the results of an OST performed after as part of a combined testing protocol.…”

Section: Introductionmentioning

confidence: 99%

Effect of thyrotropin‐releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol

Hodge

Kowalski

Torcivia

et al. 2019

Self Cite

Background The use of parallel dynamic tests to identify insulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID) in horses could have better diagnostic utility than measuring baseline hormone concentrations, if the tests do not alter diagnostic interpretation of one another. Hypothesis Performing a thyrotropin‐releasing hormone (TRH) stimulation test before an oral sugar test (OST) would not affect results of OST. Animals Twenty‐six healthy university‐owned horses. Methods A prospective randomized placebo‐controlled, crossover design was used to evaluate 3 OST protocols: OST alone, TRH followed by OST (TRH + OST), and placebo followed by OST (placebo + OST). Agreement for plasma insulin concentrations and diagnostic interpretation were assessed with Bland‐Altman and logistic regression analyses, respectively. Results Bland‐Altman analysis of TRH + OST versus OST alone showed good agreement between testing protocols, with bias ± SD for insulin concentrations at baseline 0.4 ± 4.7 μIU/mL (95% limits of agreement [LOA], −8.8 to 9.7), 60 minute −0.5 ± 22.6 μIU/mL (95% LOA, −44.7 to 43.8), and 90 minute 1.9 ± 20.6 μIU/mL (95% LOA, −38.5 to 42.4) after OST, similar to placebo + OST versus OST alone. Diagnostic interpretation (positive/negative) was not different between protocols (TRH + OST versus OST alone [P = .78], placebo + OST versus OST alone [P = .77], or TRH + OST versus placebo + OST [P = .57]). Conclusions and Clinical Importance Concurrent testing for PPID and ID with a TRH stimulation test before an OST is an acceptable diagnostic tool for investigation of endocrinopathies in horses and allows accurate testing to be performed efficiently in 1 visit.

“…Similarly, in horses suffering from PPID, higher rates of therapeutic failure have been observed when ID is unrecognized . One previous study has investigated the combination of the TRH stimulation test and the OST . However, PO administration of glucose to horses significantly impacted their plasma ACTH concentrations after TRH injection .…”

Section: Introductionmentioning

confidence: 99%

“…One previous study has investigated the combination of the TRH stimulation test and the OST . However, PO administration of glucose to horses significantly impacted their plasma ACTH concentrations after TRH injection . Therefore, our aim was to investigate the diagnostic value of the TRH stimulation test and the 2‐step insulin sensitivity test performed in combination to provide a diagnostic protocol for PPID and ID simultaneously.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of combined testing to simultaneously diagnose pituitary pars intermedia dysfunction and insulin dysregulation in horses

Horn

Bertin

2019

Background The thyrotropin‐releasing hormone (TRH) stimulation test and the 2‐step insulin sensitivity test are commonly used methods to diagnose, respectively, pituitary pars intermedia dysfunction (PPID) and insulin dysregulation (ID). Objectives To investigate the diagnostic value of combining the TRH stimulation test and the 2‐step insulin sensitivity test to diagnose PPID and ID simultaneously. Animals Twenty‐seven adult horses, 10 control horses without PPID or ID, 5 horses with PPID only, 5 horses with ID only, and 7 horses with PPID and ID. Methods Randomized prospective study. Horses underwent a TRH stimulation test alone, a 2‐step insulin sensitivity test alone, and combined testing with simultaneous TRH and insulin injection in the same syringe. Data were compared by 2‐way repeated measures analysis of variance and 2 1‐sided tests to demonstrate equivalence. Bland‐Altman plots were generated to visualize agreement between combined and independent testing. Results The effect of combined testing on plasma adrenocorticotropic hormone, blood glucose concentration, or percentage decrease in blood glucose concentration was not significantly different from the effect obtained with independent testing. One control horse appeared falsely positive for PPID, 2 PPID‐only horses appeared falsely positive for ID, and 1 PPID and ID horse appeared falsely negative for ID when tests were performed simultaneously. Bland‐Altman plots supported the agreement between combined and independent testing. Conclusions and Clinical Importance Combining the TRH stimulation test and the 2‐step insulin sensitivity test appears to be a useful diagnostic tool for equine practitioners in the field, allowing testing of a horse for both PPID and ID simultaneously.