Phenotypic, hormonal, and clinical characteristics of equine endocrinopathic laminitis

Abstract

Background Equine endocrinopathic laminitis is common and can be associated with an underlying endocrinopathy, such as equine metabolic syndrome (EMS), pituitary pars intermedia dysfunction (PPID), pasture consumption, or any combination of these factors. Objectives The aim of the study was to improve the risk assessment capabilities of clinicians, and to inform management strategies, for acute endocrinopathic laminitis by prospectively examining the phenotypic, hormonal, and clinical characteristics of the disease in a large cohort. Animals Privately owned horses and ponies (n = 301) of any age, sex, or breed diagnosed with laminitis by a veterinarian. A history of laminitis was acceptable. Methods This was a prospective cohort study. Veterinarians provided information on each case via an online questionnaire after informed consent from the animal's owner, and all data were de‐identified before analysis. Serum insulin and plasma adrenocorticotrophic hormone concentrations were measured in each case. Results Most cases were recruited in spring (109/301; 36.2%). Concurrent EMS and PPID resulted in higher basal insulin concentrations (49 [21.5‐141]; P < .02) than if an animal had a single underlying cause for their laminitis. The insulin concentration was negatively correlated (r 2 = −0.38; P < .001) with the animal's height, being higher in ponies (33[10‐14]; P < .001) than horses (9.5 [3‐25.7]) and was positively correlated (r 2 = 0.12; P = .05) with their grade (severity) of laminitis. Conclusions and Clinical Importance Horses and ponies with concurrent endocrinopathies have more marked hyperinsulinemia. Higher basal insulin concentrations were associated with more severe lameness.

Incidence and risk factors for recurrence of endocrinopathic laminitis in horses

“…The endocrinopathic causes for laminitis that were identified included EMS (n = 248), PPID (n = 113), and pasture‐associated laminitis (n = 95). Of the 301 animals, 134 (45%) had more than 1 of these factors …”

“…Potential participants were then directed to a study web site, which provided all details pertinent to involvement, including how to access free laboratory tests. Cases were accepted within 4 weeks of their laminitis episode over a 2‐year period, and each case was followed up for 2 years after inclusion. The veterinarian completed a detailed questionnaire about the animal, and owners provided consent for their animal to be included in the study.…”

“…The veterinarian completed a detailed questionnaire about the animal, and owners provided consent for their animal to be included in the study. Veterinarians reported on animal factors, including signalment, history, Obel grade of lameness and clinical signs of the disease, including the presence or absence of digital pulses, a positive response to hoof testers, founder rings or hoof deformity or both, as well as geographic factors (location and season), and any treatments and management strategies . The animals might have had previous episodes of laminitis and could be of any signalment (except donkeys).…”

“…Given that endocrinopathic laminitis is the most common form of the disease; each case of laminitis was designated to be either endocrinopathic or non‐endocrinopathic in origin. The criteria used for classification of the cases have been reported previously . Briefly, these were elevated resting serum insulin concentration (>20 μIU/mL), elevated plasma ACTH concentration (considered to have PPID if >35 pg/mL or > seasonally adjusted, location‐specific reference ranges during autumn), body condition score (BCS) ≥ 6/9, cresty neck score (CNS) ≥ 2/5, other evidence of regional adiposity, history of recent access to pasture, sudden increase in nonstructural carbohydrate (NSC) content of the diet (in the absence of diarrhea or colic), breed at‐risk of EMS, being an easy‐keeper, divergent growth rings in 1 or more hoof wall, a familial history of laminitis, and a dysregulated post‐prandial serum insulin response to an oral glucose test (OGT) or an oral sugar test (OST).…”

“…If 2 or more of the criteria were met, or 1 criterion in the absence of an obvious non‐endocrine cause for laminitis, the case was classified as endocrinopathic in origin. The presence of an endocrine disease and a history of recent exposure to pasture was previously evaluated in each animal, with cases deemed to have PPID, EMS or pasture‐associated laminitis, or a combination of factors.…”