Evaluation of a thyrotropin-releasing hormone solution stored at room temperature for pituitary pars intermedia dysfunction testing in horses

Goodale, Lindsay; Frank, Nicholas; Hermida, Pilar; D'Oench, Sarah

doi:10.2460/ajvr.76.5.437

Cited by 9 publications

(8 citation statements)

References 19 publications

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“…After clinical examination study horses were humanly euthanized with Na pentobarbital (100 mg/kg, IV). Pituitary glands were collected and sectioned along a midline sagittal plane within less than 1 h after euthanasia, as described 56 . One half of the pituitary gland was immediately placed on ice and frozen (−86 °C) and the other half was immersed in 100 mL of 10% neutral buffered formalin and fixed at room temperature for ≥ 72 h. All procedures were approved by the Michigan State University Institutional Animal Care and Use Committee (PROTO201900231).…”

Section: Methodsmentioning

confidence: 99%

Equine pituitary pars intermedia dysfunction: a spontaneous model of synucleinopathy

Fortin

Hetak

Duggan

et al. 2021

Sci Rep

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Equine pituitary pars intermedia dysfunction (PPID) is a common endocrine disease of aged horses that shows a similar pathophysiology as Parkinson’s Disease (PD) with increased levels of α-synuclein (α-syn). While α-syn is thought to play a pathogenic role in horses with PPID, it is unclear if α-syn is also misfolded in the pars intermedia and could similarly promote self-aggregation and propagation. Consequently, α-syn was isolated from the pars intermedia from groups of healthy young and aged horses, and aged PPID-afflicted horses. Seeding experiments confirmed the prion-like properties of α-syn isolated from PPID-afflicted horses. Next, detection of α-syn fibrils in pars intermedia via transmission electron microscopy (TEM) was exclusive to PPID-afflicted horses. A bank of fragment peptides was designed to further characterize equine α-syn misfolding. Region 62–87 of equine and human α-syn peptides was found to be most prone to aggregation according to Tango bioinformatic program and kinetics of aggregation via a thioflavin T fluorescence assay. In both species, fragment peptide 62–87 is capable of generating mature fibrils as demonstrated by TEM. The combined animal, bioinformatic, and biophysical studies provide evidence that equine α-syn is misfolded in PPID horses.

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Section: Methodsmentioning

confidence: 99%

Equine pituitary pars intermedia dysfunction: a spontaneous model of synucleinopathy

Fortin

Hetak

Duggan

et al. 2021

Sci Rep

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“…Over the last decade, many refinements to TRH stimulation testing have been investigated to improve sensitivity of PPID diagnosis and augment practical clinical utility. [5][6][7][8][9][10] The Equine Endocrinology Group recommends the TRH stimulation test and provides interpretation criteria for diagnosis of PPID based on the ACTH concentration of a plasma sample obtained 10 minutes after intravenous administration of TRH. 11 TRH stimulation testing produces an exaggerated ACTH release in horses with PPID because of presence of TRH receptors located within hyperplastic tissue of the pars intermedia of the pituitary.…”

Section: Pituitary Pars Intermedia Dysfunction (Ppid Previously Known...mentioning

confidence: 99%

“…Over the last decade, many refinements to TRH stimulation testing have been investigated to improve sensitivity of PPID diagnosis and augment practical clinical utility. 5 , 6 , 7 , 8 , 9 , 10 The Equine Endocrinology Group recommends the TRH stimulation test and provides interpretation criteria for diagnosis of PPID based on the ACTH concentration of a plasma sample obtained 10 minutes after intravenous administration of TRH. 11…”

Section: Introductionmentioning

confidence: 99%

“…This dynamic test can offer the possibility of earlier diagnosis or confirmation of PPID in horses with suggestive clinical signs but equivocal or normal basal ACTH concentrations. Over the last decade, many refinements to TRH stimulation testing have been investigated to improve sensitivity of PPID diagnosis and augment practical clinical utility 5‐10 . The Equine Endocrinology Group recommends the TRH stimulation test and provides interpretation criteria for diagnosis of PPID based on the ACTH concentration of a plasma sample obtained 10 minutes after intravenous administration of TRH 11…”

Section: Introductionmentioning

confidence: 99%

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Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses

Thane

Uricchio

Frank

2022

Veterinary Internal Medicne

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Background Diagnosis of pituitary pars intermedia dysfunction (PPID) using the thyrotropin‐releasing hormone (TRH) stimulation test requires blood collection 10 minutes after TRH injection; it is unknown if small differences in timing affect test results. Objective To determine whether early or late sampling results in a significant (≥10%) difference in plasma adrenocorticotropic hormone (ACTH) concentration compared to standard 10‐minute sampling. Animals Twenty‐four healthy adult horses with unknown PPID status. Methods In this prospective study, subjects underwent a single TRH stimulation test, with blood collected exactly 9 minutes (early), 10 minutes (standard), and 11 minutes (late) after injection. ACTH was measured by chemiluminescent immunoassay. Two aliquots of the 10‐minute plasma sample were analyzed separately to assess intra‐assay variability. Data were reported descriptively and bias was calculated using Bland‐Altman plots. Significance was set at P = .05. Results Minor variability was observed between the paired 10‐minute sample aliquots (range, 0%‐6%; median 3%). Overall variability of early or late samples compared to the corresponding paired (average) 10‐minute standard concentration ranged from 0% to 92% (median 10%). Seventy‐five percent of horses (18/24) tested had at least 1 early or late reading that differed by ≥10% from its corresponding 10‐minute standard concentration, and 21% of horses (5/24) would have a different interpretation of testing result with either early or late sampling. Incidence of ≥10% variability was independent of PPID status (P = .59). Conclusions and Clinical Importance Precise timing of sample collection is critical to ensure accurate assessment of PPID status given the observation of significant variability associated with minor alterations in timing of sample collection.

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“…The TRH stimulation test is now a recommended test to diagnose early PPID (Equine Endocrinology Group website, available at: http://sites.tufts.edu/equinendogroup, accessed January 10, 2019). In addition to its increased sensitivity, this test can be performed within 30 minutes, and because TRH has been shown to be stable at room temperature, the test could be used in practice …”

Section: Introductionmentioning

confidence: 99%

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

Horn

Bertin

2019

Veterinary Internal Medicne

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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.

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Evaluation of a thyrotropin-releasing hormone solution stored at room temperature for pituitary pars intermedia dysfunction testing in horses

Abstract: Results indicated that the TRH stimulation test should not be repeated within 24 hours, and cTRH solution stored at room temperature could be used to effectively perform TRH stimulation testing in horses.

Cited by 9 publications

References 19 publications

Equine pituitary pars intermedia dysfunction: a spontaneous model of synucleinopathy

Equine pituitary pars intermedia dysfunction: a spontaneous model of synucleinopathy

Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses

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

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