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Equine pituitary pars intermedia dysfunction: current perspectives on diagnosis and management

Authors Spelta C

Received 12 May 2015

Accepted for publication 2 July 2015

Published 20 August 2015 Volume 2015:6 Pages 293—300

DOI https://doi.org/10.2147/VMRR.S74191

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Professor Wael EL-Deeb

Peer reviewer comments 2

Editor who approved publication: Professor Young Lyoo


Caroline W Spelta

Townsville Vet Clinic, Townsville, QLD, Australia

Abstract: Equine pituitary pars intermedia dysfunction (PPID) is a neurodegenerative disease of the hypothalamus, resulting in the loss of dopaminergic inhibition of pars intermedia. An oxidative stress injury of unknown etiology has been suggested to initiate the neurodegeneration. While hypertrichosis (formerly known as hirsutism) is considered pathognomic for advanced disease, the antemortem diagnosis of subclinical and early disease has continued to prove difficult. Numerous tests have been used with varying sensitivities and specificities. The overnight dexamethasone suppression test, originally documented to have 100% sensitivity and specificity in horses with advanced disease, has proven to be less valuable in identifying early disease. Basal plasma adrenocorticotropin concentrations have improved sensitivity and specificity when sampled during the autumn months, and α-melanocyte-stimulating hormone, while not yet commercially available, shows promise as a sensitive and specific single sample test. Recent advances in our knowledge include the strong association between laminitis and hyperinsulinemia, both common clinical signs associated with PPID. The pathogenesis of hyperinsulinemia, laminitis, and their association with this disease is a focus of current research. The dopamine agonist pergolide mesylate is still the mainstay of medical management, with studies on oral bioavailability, pharmacokinetics, and long-term survival rates now published.

Keywords: PPID, ACTH, α-MSH, laminitis, pergolide, hypertrichosis, pars pituitary intermedia dysfunction

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