Ivermectin performance in horses diagnosed with equine endocrine disorders.

Anthelmintic performance against equine cyathostomins can be evaluated by two different non-terminal measures; the Fecal Egg Count Reduction Test (FECRT) and the Egg Reappearance Period (ERP). Most available FECRT and ERP data have been determined in populations of young horses, and very little information is available from mature and senior horses. Furthermore, it is unknown how commonly occurring equine endocrine disorders such as Insulin dysregulation (ID) and Pituitary pars intermedia dysfunction (PPID) may interfere with these measurements, but it has been suggested that horses with these conditions could be more susceptible to parasitic infections. A research population of senior horses and horses with or without PPID, ID, or both were enrolled in this study. All strongylid egg count positive horses were included in an ivermectin (200 µg/kg) efficacy study. These were distributed among the following groups: ID: six, PPID: three, PPID and ID: seven, and healthy controls: three. Strongylid fecal egg counts were determined on the day of ivermectin administration, at two weeks post deworming, and on weekly intervals until eight weeks post treatment. Determination of FECRT and ERP were carried out following World Association for the Advancement of Veterinary Parasitology guidelines. Results revealed high ivermectin efficacy with mean egg count reduction at 99.7% or above in all groups at two weeks post treatment. Egg reappearance was documented at six and seven weeks in the ID and PPID/ID groups, respectively, whereas the PPID and healthy control groups both had ERP at 8 weeks. Statistical analysis found no significant differences in egg count levels between groups during the study. The expected ERP for ivermectin is 8-10 weeks, meaning that two of the groups displayed shortened ERPs. However, due to the small group sizes, these data should be interpreted with caution. Nonetheless, results do indicate a need for further investigation of the possible influence of endocrine disorders on anthelmintic performance in horses.

Insulin, but not adiponectin, is detectable in equine saliva using an automated, commercial assay.

BACKGROUND: The hormones insulin and adiponectin are commonly measured in equids because of their involvement in endocrinopathic laminitis. These are currently measured in serum/plasma, although jugular venipuncture can cause stress in some animals and may be impossible in needle-shy individuals. However, both hormones can be measured in saliva in other species. OBJECTIVES: To determine whether [insulin] and [total adiponectin] are detectable in equine saliva using automated assays and whether saliva collection is associated with changes in stress indicators. Additionally, the correlation between serum and salivary [insulin] was investigated. STUDY DESIGN: In vivo experiment. METHODS: Paired blood and saliva samples were collected from eight adult ponies at multiple time-points (n = 45 paired samples). [Insulin] and [total adiponectin] were measured using automated assays validated for equine serum/plasma. Blink rates and heart rates were determined, using video recordings and a wearable heart rate monitor respectively, to assess the effects of sample collection on stress indicators compared with a control situation without a stressful stimulus. RESULTS: [Total adiponectin] was undetectable in saliva. However, salivary [insulin] was measurable with acceptable inter-assay (1.3 ± 0.9%) and intra-assay (1.1 ± 0.6%) variability. Blink and heart rates during saliva collection did not differ significantly from those in the control setting. Serum and salivary [insulin] were not significantly correlated. MAIN LIMITATIONS: Small sample size comprising native UK ponies; potential sampling bias as animals were recruited to the study partly based on their behaviour during blood sampling; saliva collected from unfasted animals. CONCLUSIONS: Insulin is measurable in equine saliva using an automated assay currently available in the UK, but further validation and the determination of specific diagnostic thresholds are required. Saliva collection was not associated with changes in stress indicators. Further research is therefore needed to determine the potential of equine saliva as a non-invasive alternative to blood for insulin determination.

Diagnosis of equine endocrinopathies: The value of measuring blood glucose during an oral glucose test.

Blood glucose concentration is often measured during an oral glucose test (OGT), but is not thought to aid in diagnosing insulin dysregulation (ID) or pituitary pars intermedia dysfunction (PPID). The aim of this retrospective study was to investigate whether the change in blood glucose concentration during an OGT aligned with indicators of equine metabolic syndrome or PPID, including serum insulin and plasma ACTH concentrations, clinical observations, age, sex, breed type and the test dose. The cohort included 149 horses, miniature horses, and ponies that had undergone an in-feed OGT and clinical examination between 2015 and 2021. The animals were diagnosed as either metabolically healthy, insulin-dysregulated, having PPID or both endocrinopathies. The mean ± standard error increase in blood glucose during the OGT was 3.41 ± 0.21 mM, and this change showed a weak positive correlation with the increase in serum insulin concentration (r = 0.36; P 0.001), body condition score (BCS; r = 0.26; P = 0.002) and cresty neck score (CNS; r = 0.38; P 0.001). The median [interquartile range] increase in blood glucose for miniature horses (5.25 [2.98-6.5] mM), was more than twice that seen in full-sized horses (2.4 [1.33-3.45] mM; P = 0.03). In metabolically healthy animals the increase in blood glucose during an OGT (+2.2 [1-3.5] mM) was smaller (P 0.001) than in animals with ID (+3.8 [2.73-5.33] mM), or both endocrine diseases (+6.1 [3.6-6.85] mM). There was an effect of the dose of dextrose on the blood glucose response, with higher doses yielding larger responses (P 0.001). The variability in these data support that basal and post-prandial blood glucose responses to an OGT are not appropriate as stand-alone diagnostic markers of ID or PPID. However, the association between blood glucose and CNS supports the use of CNS when evaluating animals for ID.

Equine Endocrine Disease: Challenges With Case Definition for Research.

Equine endocrine disease is an important area for equine research, requiring an appropriate case definition for inclusion and criteria for exclusion from disease. Defining a case for research may be different from criteria for clinical diagnosis. Further, clinical diagnosis recommendations have been changing regularly, making this area challenging for equine scientists. This review discusses the diagnosis of major equine endocrine diseases, pituitary pars intermedia dysfunction, equine metabolic syndrome and insulin dysregulation, focusing on the most appropriate diagnostic methods for research case definitions. Different diagnostic methods, including use of reference intervals and clinical decision limits, will be discussed with their relative merits for use in case definition for research.

A review of cellular and molecular mechanisms in endocrinopathic, sepsis-related and supporting limb equine laminitis.

Equine laminitis has both fascinated and frustrated veterinary researchers and clinicians for many years. The recognition that many ponies suffering from pasture-associated laminitis have an insulin-dysregulated phenotype (endocrinopathic laminitis, EL) and that prolonged insulin and glucose infusions can experimentally induce laminar pathology and functional failure are seminal discoveries in this field. Researchers have studied the molecular basis for disease pathogenesis in models of EL, sepsis-related laminitis and supporting limb laminitis and generated much data over the last 15 years. This review attempts to synthesise those data, drawing comparisons between models and naturally occurring laminitis. A hypothesis is proposed that the basal epithelial cell stress is a central event in each category of laminitis. Furthermore, in naturally occurring pasture-associated laminitis, pathways that predominate in each type of laminitis contribute to laminar lamellar pathology to varying extents. Based on the molecular mechanisms determined in experimental models, interactions between these pathways are identified.

The effect of season, management and endocrinopathies on vitamin D status in horses.

BACKGROUND: Vitamin D deficiency is common in humans and is increasingly linked to the pathogenesis of a multitude of diseases including obesity and metabolic syndrome. The biology of vitamin D in horses is poorly described; the relative contribution of the diet and skin synthesis to circulating concentrations is unclear and associations with the endocrine disease have not been explored. OBJECTIVES: To determine the relationship between management, season and endocrine disease and vitamin D status in horses. STUDY DESIGN: Cross-sectional cohort study. METHODS: Plasma concentrations of 25-hydroxyvitamin D2 (25(OH)D2 ) and D3 (25(OH)D3 ) were measured by liquid chromatography-tandem mass spectrometry in 34 healthy unsupplemented grazing ponies and 22 stabled Thoroughbreds receiving supplementary vitamin D3 in feed. A nested group of 18 grazing ponies were sampled on long and short days (>12 and <12 h of light/day) to determine the effect of sunlight exposure. In addition, the relationships between age, sex, adiposity, serum insulin, adrenocorticotropic hormone and vitamin D status were assessed in a mixed group of 107 horses using a linear regression model. RESULTS: All animals had a measurable level of 25(OH)D2 (median 10.7 nmol/L) whilst 25(OH)D3 was only detected in Thoroughbreds receiving D3 supplementation. Thoroughbreds had lower concentrations of 25(OH)D2 than ponies (7.4 vs. 12.6 nmol/L, p < 0.01). In grazing ponies, 25(OH)D2 concentrations were significantly higher on long days compared to short days (14.4 vs. 8.7 nmol/L, p < 0.01), whilst 25(OH)D3 was undetectable. Measures of increased adiposity, but not basal insulin, were associated with higher 25(OH)D2 concentrations, conversely to humans. Increasing ACTH was associated with lower 25(OH)D2 (p < 0.01). MAIN LIMITATIONS: Vitamin D2 concentrations were not measured in grass or forage. CONCLUSIONS: In horses 25(OH)D2 is the predominant vitamin D metabolite, and there is an apparent lack of endogenous vitamin D3 production. The relationship between vitamin D and endocrine disorders in horses does not reflect that of other species and warrants further investigation.

A one-health approach to identifying and mitigating the impact of endocrine disorders on human and equine athletes.

Endocrinopathies affect multiple species in ever-increasing percentages of their populations, creating an opportunity to apply one-health approaches to determining creative preventative measures and therapies in athletes. Obesity and alterations in insulin and glucose dynamics are medical concerns that play a role in whole-body health and homeostasis in both horses and humans. The role and impact of endocrine disorders on the musculoskeletal, cardiovascular, and reproductive systems are of particular interest to the athlete. Elucidation of both physiologic and pathophysiologic mechanisms involved in disease processes, starting in utero, is important for development of prevention and treatment strategies for the health and well-being of all species. This review focuses on the unrecognized effects of endocrine disorders associated with the origins of metabolic disease; inflammation at the intersection of endocrine disease and related diseases in the musculoskeletal, cardiovascular, and reproductive systems; novel interventions; and diagnostics that are informed via multiomic and one-health approaches. Readers interested in further details on specific equine performance conditions associated with endocrine disease are invited to read the companion Currents in One Health by Manfredi et al, JAVMA, February 2023.

Endocrine Diagnostics for Exotic Animals.

Endocrine disease in exotic species is less common than in small animals. Nevertheless, the diagnostic principles used in small animals can be adapted to evaluate endocrine disease in many of the exotic species although species-specific aspects need to be considered. This article covers important diseases such as thyroid dysfunction in reptiles and birds, hyperthyroidism in guinea pigs, and hyperadrenocorticism in ferrets. Glucose metabolism in neoplasms affecting normal physiology, such as insulinoma in ferrets and gastric neuroendocrine carcinoma in bearded dragons, is discussed. Calcium abnormalities, including metabolic bone disease in reptiles and hypocalcemia in birds, are also covered.

Approaches to endocrinopathic laminitis in the field: Results of a survey of veterinary practitioners in North America.

Endocrinopathic laminitis is the most common cause of laminitis in the field. Insulin has recently been implicated as a key factor in development of endocrinopathic laminitis; however, it is unclear whether diagnostic, and treatment approaches reflect insights derived from recent research. This study sought to evaluate North American veterinary practitioners' approach to endocrinopathic laminitis in the field. Demographic information, approach to diagnosis, management, and prognosis of endocrinopathic laminitis, as well as factors influencing changes in approach to laminitis were collected. To compare regional differences in approach to laminitis, results were compared to a recently published study from the United Kingdom. Findings of the present study suggest that North American practitioners have changed their approach to laminitis to more readily incorporate diagnostic testing for endocrine disease.

Endocrinopathic Laminitis.

Endocrinopathic laminitis (EL) primarily occurs because of insulin dysregulation (ID) mediated through downstream effects of insulin on IGF-1R in lamellar tissues. There is likely contributing vascular and metabolic dysfunction within the lamellae, but EL is relatively non-inflammatory. EL is associated with lamellar stretching, proliferation, and failure, ultimately causing failure of the suspensory apparatus of the distal phalanx. Proper education regarding mitigating risk factors makes this a largely preventable cause of laminitis. Annual hoof evaluation plus screening geriatric horses for pituitary pars intermedia dysfunction and ID, and younger horses for ID, can significantly decrease the incidence of this devastating condition.

Influence of endocrine disease on l-lactate concentrations in blood of ponies.

BACKGROUND: Blood l-lactate concentrations are higher in people with developing or established diabetes mellitus and insulin resistance. OBJECTIVES: To investigate whether blood l-lactate concentrations are positively correlated with measures of insulin dysregulation (ID) or increased autumnal ACTH concentrations in ponies. ANIMALS: Systemically healthy client-owned ponies (n = 101). METHODS: Prospective case-control study. Blood samples were obtained from 101 clinically healthy ponies. Breed, weight, height, and subjective and objective measures of body condition were recorded. Blood l-lactate, glucose, triglyceride, total adiponectin, and ACTH concentrations were measured and an oral sugar test (OST) was carried out. Correlations between blood l-lactate and variables of endocrine health were determined. RESULTS: Using a seasonal cutoff point of ACTH concentrations ≥47 pg/mL, 55 ponies had increased autumnal ACTH concentrations and 45 did not. Using a basal insulin concentration of >50 µiU/mL, 42 ponies were diagnosed with ID and 58 were not. Using a 60 minutes after OST cutoff point of >45 µiU/mL, 57 ponies had ID and 37 did not. Blood l-lactate concentrations were significantly lower in obese (average body condition score ≥ 7/9) compared to nonobese ponies (0.6 mmol/L; range, 0.0-1.9 mmol/L vs 0.8 mmol/L; range, 0.3-2.7 mmol/L; P = .01). No other significant correlations were detected. No differences were detected between ponies with and without increased autumnal ACTH concentrations (0.7 mmol/L; range, 0.0-2.7 mmol/L vs 0.7 mmol/L; range, 0.3-1.8 mmol/L; P = .84) and with and without ID (0.7 mmol/L; range, 0.3-2.7 mmol/L vs 0.8 mmol/L; range, 0.0-1.6 mmol/L; P = .63). CONCLUSIONS AND CLINICAL IMPORTANCE: Results do not support an effect of endocrine status on l-lactate concentrations in blood of ponies.

Translating research into practice: Adoption of endocrine diagnostic testing in cases of equine laminitis.

Research demonstrating insulin's causal role in endocrinopathic laminitis has greatly advanced understanding of equine laminitis. However, the degree to which this knowledge has been translated into clinical practice has not been assessed. This two-part study aimed to investigate veterinary surgeons' current diagnostic approach to laminitis, whether this had changed over time, and the impact of diagnosing an endocrinopathy on laminitis case management and outcome. Two cross-sectional online surveys of equine veterinary surgeons working within the UK were undertaken. The first study population comprised 141 veterinary surgeons, who had graduated a median of 8 years previously. Overall, 83.6% of respondents (n = 117/140) had changed their diagnostic approach to laminitis since graduating, primarily through increasing use of endocrine testing (88.7%; n = 86/97). Ninety-nine percent (n = 140/141) performed endocrine diagnostic test(s) for some or all laminitis cases at initial and/or subsequent examinations. The second study had 120 participating veterinary surgeons, ≥76% of whom considered diagnosing underlying endocrine diseases greatly influenced their laminitis case management. Where an endocrinopathy was identified, 75.0% (n = 90/120) considered that client communication regarding laminitis was facilitated, and ≥67% considered that treating the endocrinopathy was effective in reducing laminitis recurrence. This study demonstrates successful translation of research knowledge into equine practice, with the vast majority of veterinary surgeons adopting endocrine diagnostic testing within their routine approach to laminitis cases. Respondents perceived that this change in diagnostic approach has resulted in improvements in several non-clinical and clinical healthcare outcomes, including client communication and reduction in recurrent laminitis episodes.

Laminite endocrinopática em equinos com síndrome metabólica: características clínicas, tratamento e evolução em três pacientes ˗ relato de caso / [Endocrinopathic laminitis in horses with metabolic syndrome: clinical characteristics, treatment and evolution in three patients ˗ case report]

Laminite endocrinopática designa os casos de laminite cuja etiologia está associada a uma endocrinopatia. Cavalos com síndrome metabólica equina (SME) apresentam adiposidade regional e obesidade. Existe uma correlação positiva entre obesidade e resistência à insulina. Este relato descreve três casos de laminite endocrinopática em cavalos com SME. Os pacientes apresentaram escore de condição corporal (ECC) variando de 8 a 9 (escala de 1 a 9), sensibilidade ao teste de pinçamento do casco e claudicação de grau 3 ou 4 (escala de 1 a 4). Não havia histórico de cólica recente, trauma ou excesso de exercício. O tratamento incluiu medicação anti-inflamatória não esteroidal, repouso na baia, restrição energética para perda de peso, revestimento e bandagem dos membros, conforme a necessidade de cada paciente. A restrição alimentar ajudou no tratamento da SME e reduziu o ECC. Tratamento medicamentoso, casqueamento e bandagem diminuíram o grau de claudicação. Conclui-se que o tratamento anti-inflamatório não esteroidal, a restrição energética, o repouso em baia, o casqueamento e a bandagem do casco são eficazes no tratamento da laminite endocrinopática em cavalos com síndrome metabólica equina.(AU)

Endocrinopathic laminitis refers to cases of laminitis whose etiology is associated with an endocrinopathy. Horses with Equine Metabolic Syndrome (EMS) have regional adiposity and obesity. There is a positive correlation between obesity and insulin resistance. This report describes three cases of endocrinopathic laminitis in horses with EMS. Patients had body condition score (BCS) ranging from 8 to 9 (scale from 1 to 9), sensitivity to the hoof clamping test and claudication grade 3 or 4 (scale from 1 to 4). There was no history of recent colic, trauma or over exercise. Treatment included non-steroidal anti-inflammatory medication, stall rest, energy restriction for weight loss, hoofing and hoof bandage as needed by each patient. Dietary restriction helped in the treatment of EMS and reduced BCS. Drug treatment, hoofing and hoof bandage decreased the degree of lameness. It is concluded that non-steroidal anti-inflammatory treatment, energy restriction, stall rest, hoofing and hoof bandage are effective in the treatment of endocrinopathic laminitis in horses with equine metabolic syndrome.(AU)

Genetics of Equine Endocrine and Metabolic Disease.

A role for a genetic contribution to equine metabolic syndrome (EMS) and pars pituitary intermedia dysfunction (PPID) has been hypothesized. Heritability estimates of EMS biochemical measurements were consistent with moderately to highly heritable traits. Further, genome-wide association analyses have identified hundreds of regions of the genome contributing to EMS and candidate variants have been identified. The genetics of PPID has not yet been proven. Continued research for the specific genetic risk factors for both EMS and PPID is crucial for gaining a better understanding of the pathophysiology of both conditions and allowing development of genetic tests.

Infecção de trato urinário inferior por Citrobacter sp em cadela com hipoadrenocorticismo / Citrobacter sp lower urinary tract infection in a bitch with hypoadrenocorticism

Citrobacter sp. é um microrganismo frequentemente encontrado em vagina de cadelas, mas corresponde a menos de 3% do total de microrganismos isolados em urocultura. O hipoadrenocorticismo (HA) é uma doença endócrina incomum e que leva a poliúria e hipostenúria. O objetivo deste trabalho é relatar o caso de uma fêmea da espécie canina, da raça Teckel, 11 anos, atendida com queixa de urina de odor alterado há vários dias, além de vômito, diarreia e inapetência há três dias, e poliúria e polidipsia há 2 meses, com histórico de tratamento anterior com mitotano para hiperadrenocorticismo. O diagnóstico foi de ITU por Citrobactersp., além de HA iatrogênico. Como destaques nos exames, relação sódio:potássio de 22,6 foi observada, sugestiva de HA, que foi confirmado por teste de estimulação com ACTH, além de urina inicialmente hipostenúrica (densidade 1,006), o que pode ser atribuído ao washout medular renal devido à hiponatremia causada pelo hipoadrenocorticismo. O tratamento foi feito com amoxicilina associada a ácido clavulânico por 20 dias, além da terapia específica para HA com prednisona e fludrocortisona, que foi continuado. A paciente recuperou-se bem, a densidade urinária aumentou após início do tratamento para HA e não houve recidiva da ITU em período de acompanhamento de 8 meses. Acredita-se que a baixa densidade urinária causada pelo HA tenha sido fator essencial para a ocorrência da ITU por Citrobacter.

Citrobacter sp. is a normal constituent of bitches' vagina, but it is related to less than 3% of total isolated microorganism in uroculture. Hypoadrenocorticism (HA) is an endocrine disease uncommonly diagnosed that leads to polyuria and hypostenuria. The aim of this work is report the case of a Teckel bitch, 11 years old, attended with complaint of altered urinary smell for several days, besides vomiting, diarrhea and inappetence for three days, and polyuria and polydispsia for two months, with previous mitotane treatment for hyperadrenocorticism. The diagnosis was Citrobacter UTI, besides iatrogenic HA. The most important exam results include sodium:potassium ratio of 22.6, suggestive of HA, that was confirmed by ACTH stimulation test. Besides, hypostenuria (urinary specific gravity ­ USG - of 1.006) was noted, attributed to renal medular washout due to hyponatremia seen in HA. Therapy comprised amoxicillin associated with clavulanic acid for 20 days, in addition to specific therapy for AH with prednisone and fludrocortisone. The patient recovery well, USG increased after the beginning of the treatment for HA and there was no UTI reinfection for a 8 month period. It is believed that low USG due to HA was essential for the occurrence of Citrobacter UTI.

Metabolic and Endocrine Disorders in Donkeys.

The donkey evolved under harsh and arid environmental conditions, developing unique energy-efficiency traits, with an efficiency to rapidly mobilize fat in situations of increased energy demands or when food is scarce. This evolution has led to an inherent predisposition of donkeys to obesity, dyslipidemias, insulin dysregulation/metabolic syndrome, pituitary pars intermedia dysfunction, and endocrinopathic laminitis. Marked differences have been described in hormone dynamics and testing protocols for the diagnosis of these endocrine and metabolic diseases in donkeys compared with horses, underlining the necessity of a species-specific approach in order to avoid misdiagnosis, unnecessary or inadequate treatments, and additional costs.

Diagnostic Testing for Equine Endocrine Diseases: Confirmation Versus Confusion.

Despite there being only 2 common endocrine diseases in horses, pituitary pars intermedia dysfunction (PPID) and equine metabolic syndrome (EMS), diagnosis is still confusing. Failing to consider horse factors and treating based on laboratory results only have caused many animals to receive lifelong drug treatment unnecessarily. Increased plasma ACTH, baseline or TRH stimulated, supports a diagnosis of PPID; however, breed, age, thriftiness, illness, coat color, geography, diet, and season also affect ACTH concentration. Insulin dysregulation, the hallmark of EMS, can result from insulin resistance or excessive postprandial insulin release. Each requires a different diagnostic test to reach a diagnosis.

Incidence and risk factors for recurrence of endocrinopathic laminitis in horses.

BACKGROUND: Endocrinopathic laminitis is common in horses and ponies, but the recurrence rate of the disease is poorly defined. OBJECTIVES: To determine the incidence of, and risk factors for, the recurrence of endocrinopathic laminitis. ANIMALS: Privately owned horses and ponies with acute laminitis (n = 317, of which 276 cases with endocrinopathic laminitis were followed up to study completion). METHODS: This prospective cohort study collected data on veterinary-diagnosed cases of acute laminitis for 2 years. Each case was classified on acceptance to the study as endocrinopathic or non-endocrinopathic using data collected in a questionnaire completed by the animal's veterinarian. Follow-up data were collected at regular intervals to determine whether the laminitis recurred in the 2-year period after diagnosis. RESULTS: The recurrence rate for endocrinopathic laminitis was 34.1%. The risk of recurrence during the 2-year study period increased with basal, fasted serum insulin concentration (P ≤ .05), with the probability of recurrence increasing markedly as the insulin concentration increased beyond the normal range (0-20 µIU/mL) to over the threshold for normal (up to approximately 45 µIU/mL). Being previously diagnosed with laminitis (before the study; P = .05) was also a risk factor for recurrent laminitis. Cases with a higher Obel grade of laminitis were likely (P = .05) to recur sooner. CONCLUSIONS AND CLINICAL IMPORTANCE: Knowing that hyperinsulinemia and being previously diagnosed with laminitis are significant risk factors for recurrence will enable clinicians to proactively address these factors, thereby potentially reducing the risk of recurrence of laminitis.

Phenotypic, hormonal, and clinical characteristics of equine endocrinopathic laminitis.

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 (r2 = -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 (r2 = 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.