Equine Endocrine Disease: Challenges With Case Definition for Research

McGowan, Catherine; Ireland, J.L.

doi:10.1016/j.jevs.2023.104491

Cited by 3 publications

(2 citation statements)

References 45 publications

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“…The 10‐min protocol is different in this regard, as an equivocal range is included rather than a binary positive or negative test result, as was determined for the 30‐min protocol. When equivocal results are obtained, the observation of strong clinical signs or re‐testing are recommended to confirm a diagnosis 2,22 . Given that the horses in this study with an equivocal 10‐min result demonstrated supportive clinical signs, in practice these horses would have been deemed positive for the purposes of clinical management.…”

Section: Discussionmentioning

confidence: 97%

Clinical implications of imprecise sampling time for 10‐ and 30‐min thyrotropin‐releasing hormone stimulation tests in horses

Vorster,

Wang,

Kemp

et al. 2023

Equine Veterinary Journal

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BackgroundThe thyrotropin‐releasing hormone (TRH) stimulation test is used to diagnose pituitary pars intermedia dysfunction (PPID) using 10‐ or 30‐min protocols. Imprecise sampling time for the 10‐min protocol can lead to misdiagnoses.ObjectivesTo determine the effect of imprecise sampling time for the 30‐min protocol of the TRH stimulation test.Study designIn vivo experiment.MethodsPlasma immunoreactive adrenocorticotropin (ACTH) concentrations were measured 9, 10, 11, 29, 30 and 31 min after intravenous administration of 1 mg of TRH in 15 control and 12 PPID horses. Differences in ACTH concentrations between sampling times, variability in ACTH concentrations between protocols, and diagnostic classification of PPID were assessed using Friedman's test, Bland–Altman plots, and Fisher's exact test, respectively, with 95% confidence intervals reported and significance set at p < 0.05.ResultsImprecise sampling time resulted in variable ACTH concentrations, but significant differences in absolute ACTH concentrations were not detected for imprecise sampling within each protocol or between protocols. Imprecise sampling changed PPID diagnostic classification for 3/27 (11 [4–28] %) horses for both protocols. Using the 30‐min protocol as a reference, 1/12 (8 [1–35] %) horses returned a negative test result and 5/12 (42 [19–68] %) horses returned equivocal test results that would be considered positive in practice due to the presence of supportive clinical signs.Main limitationsLimited sample size and inter‐horse variability reduced the ability to detect small but potentially relevant differences.ConclusionsOverall, the impact of imprecise sampling was not significantly different between the 10‐ and 30‐min TRH stimulation test protocols. However, diagnostic classification for PPID would have varied between the 10‐ and 30‐min protocols in this population, if clinical signs had been ignored. Precise timing during TRH stimulation tests and contextual interpretation of ACTH concentrations remain fundamental for the diagnosis of PPID.

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Section: Discussionmentioning

confidence: 97%

Clinical implications of imprecise sampling time for 10‐ and 30‐min thyrotropin‐releasing hormone stimulation tests in horses

Vorster,

Wang,

Kemp

et al. 2023

Equine Veterinary Journal

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“…31 In the absence of a consensus "gold standard" for establishing a diagnosis of PPID, and likely heterogeneity in PPID-affected equids, multiple criteria were used in the present study to support a diagnosis of PPID. 32 All PPID + equids had a hypertrichosis score ≥2 and a grade 5/5 histologic PG score, criteria that most investigators would agree would support more advanced PPID.…”

Section: Conflict Of Interest Statementmentioning

confidence: 99%

Lumbar vertebral bone density is decreased in horses with pituitary pars intermedia dysfunction

Colbath,

Fortin,

Burglass

et al. 2023

Equine Veterinary Journal

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BackgroundPathological fractures have been reported in equids with pituitary pars intermedia dysfunction (PPID) but their prevalence and pathogenesis is unknown.ObjectivesTo compare: (1) bone mineral density (BMD) in weight bearing and nonweight bearing bones in PPID+ equids and aged and young PPID− controls; and (2) biomechanical properties of the fourth lumbar vertebral body in PPID+ equids and aged PPID− equids.Study designCase–control study: five PPID+ equids and six aged and four young PPID− control horses.MethodsPPID status was based on clinical signs and necropsy examination of the pituitary gland (PG). The lumbar vertebral column, right front third metacarpus (MC3), left hind third metatarsus (MT3), and PG were removed after euthanasia. BMD was determined by quantitative computed tomography of regions of interest (ROI) in each bone and biomechanical testing was performed on the fourth lumbar vertebral body. Serum concentrations of parathormone (PTH), ionised Ca++, 25‐hydroxyvitamin D, and osteocalcin (OC) were also measured. Data were analysed using one‐way ANOVA and correlation analyses.ResultsBMD of trabecular and cortical regions of interest (ROI) of the third, fourth (L4), and fifth lumbar vertebrae were significantly lower in PPID+ equids as compared with aged (p < 0. 001) and young (p < 0.01) PPID− controls. In contrast, no differences were found in BMD of trabecular or cortical ROIs of MC3 and MT3 between groups. No differences were detected in force at fracture, displacement at fracture, Young's modulus or strain of L4 between PPID+ and aged PPID− horses. No differences were found in serum PTH, ionised Ca++, 25‐hydroxyvitamin D, or OC concentrations between groups.Main limitationsLimited number of equids studied and variation in test results.ConclusionsBMD of nonweight bearing bones can be decreased with PPID and could increase risk of developing pathological fractures.

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