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Background Hypothesis/Objectives Animals Methods Results Conclusion and Clinical Importance Phenylbutazone is prescribed for laminitis‐associated pain and decreases glucose and insulin responses to an oral glucose test (OGT) in horses with insulin dysregulation (ID).Investigate the effect of phenylbutazone administration on the enteroinsular axis in horses.Sixteen horses, including 7 with ID.Randomized cross‐over study design, with horses assigned to treatment with phenylbutazone (4.4 mg/kg IV q24h) or placebo (5 mL 0.9% saline). On Day 9 of treatment, an OGT was conducted, followed by a 10‐day washout period, administration of the alternative treatment, and repetition of the OGT. Glucose‐dependent insulinotropic polypeptide (GIP), and active glucagon‐like peptide 1 and 2 (aGLP‐1 and GLP‐2) concentrations were determined by ELISA. The effects of ID status and treatment on peptide concentrations were assessed using t tests and analyses of variance.Horses with ID had significantly higher maximum GIP concentrations (Cmax) than controls (median, 279.1; interquartile range [IQR], 117.5‐319.4 pg/mL vs median, 90.12; IQR, 74.62‐116.5 pg/mL; P = .01), but no significant effect of ID was detected on aGLP‐1 and GLP‐2 concentrations. In horses with ID, phenylbutazone treatment significantly decreased GIP Cmax compared with placebo (168.1 ± 59.26 pg/mL vs 242.8 ± 121.8 pg/mL; P = .04), but no significant effect of phenylbutazone was detected on aGLP‐1 and GLP‐2 concentrations.Glucose‐dependent insulinotropic polypeptide, aGLP‐1 and GLP‐2 do not mediate the decrease in glucose and insulin concentrations observed after phenylbutazone administration. Only GIP was repeatedly associated with ID status, calling into question the role of the enteroinsular axis in ID. [ABSTRACT FROM AUTHOR]

Abstract Background Phenylbutazone is often prescribed to manage pain caused by hyperinsulinemia‐associated laminitis, but in diabetic people nonsteroidal anti‐inflammatory drugs increase insulin secretion and pancreatic activity. Hypothesis/Objectives Investigate the effect of phenylbutazone administration on insulin secretion in horses. It was hypothesized that phenylbutazone will increase insulin secretion in horses with insulin dysregulation (ID). Animals Sixteen light breed horses, including 7 with ID. Methods Randomized cross‐over study design. Horses underwent an oral glucose test (OGT) after 9 days of treatment with phenylbutazone (4.4 mg/kg IV q24h) or placebo (5 mL 0.9% saline). After a 10‐day washout period, horses received the alternative treatment, and a second OGT was performed. Insulin and glucose responses were compared between groups (ID or controls) and treatments using paired t test and analyses of variance with P

Background: Phenylbutazone is often prescribed to manage pain caused by hyperinsulinemia‐associated laminitis, but in diabetic people nonsteroidal anti‐inflammatory drugs increase insulin secretion and pancreatic activity. Hypothesis/Objectives: Investigate the effect of phenylbutazone administration on insulin secretion in horses. It was hypothesized that phenylbutazone will increase insulin secretion in horses with insulin dysregulation (ID). Animals: Sixteen light breed horses, including 7 with ID. Methods: Randomized cross‐over study design. Horses underwent an oral glucose test (OGT) after 9 days of treatment with phenylbutazone (4.4 mg/kg IV q24h) or placebo (5 mL 0.9% saline). After a 10‐day washout period, horses received the alternative treatment, and a second OGT was performed. Insulin and glucose responses were compared between groups (ID or controls) and treatments using paired t test and analyses of variance with P <.05 considered significant. Results: In horses with ID, phenylbutazone treatment significantly decreased glucose concentration (P =.02), glucose area under the curve (2429 ± 501.5 vs 2847 ± 486.1 mmol/L × min, P =.02), insulin concentration (P =.03) and insulin area under the curve (17 710 ± 6676 vs 22 930 ± 8788 μIU/mL × min, P =.03) in response to an OGT. No significant effect was detected in control horses. Conclusion and Clinical Importance: Phenylbutazone administration in horses with ID decreases glucose and insulin concentrations in response to an OGT warranting further investigation of a therapeutic potential of phenylbutazone in the management of hyperinsulinemia‐associated laminitis beyond analgesia. [ABSTRACT FROM AUTHOR]

Abstract Background Sirolimus, a mechanistic target of rapamycin inhibitor, suppresses insulin production in other species and has therapeutic potential for hyperinsulinemia in horses. Hypothesis/Objective Determine the pharmacokinetics (PKs) of sirolimus and evaluate its effect on insulin dynamics in healthy and insulin dysregulation (ID) horses. Animals Eight Standardbred geldings. Methods A PK study was performed followed by a placebo‐controlled, randomized, crossover study. Blood sirolimus concentrations were measured by liquid chromatography‐mass‐spectrometry. PK indices were estimated by fitting a 2‐compartment model using nonlinear least squares regression. An oral glucose test (OGT) was conducted before and 4, 24, 72, and 144 hours after administration of sirolimus or placebo. Effects of time, treatment and animal on blood glucose and insulin concentrations were analyzed using mixed‐effects linear regression. Sirolimus was then administered to 4 horses with dexamethasone‐induced ID and an OGT was performed at baseline, after ID induction and after 7 days of treatment. Results Median (range) maximum sirolimus concentration was 277.0 (247.5‐316.06) ng/mL at 5 (5‐10) min and half‐life was 3552 (3248‐4767) min. Mean (range) oral bioavailability was 9.5 (6.8‐12.4)%. Sirolimus had a significant effect on insulin concentration 24 hours after a single dose: median (interquartile range) insulin at 60 min (5.0 [3.7‐7.0] μIU/mL) was 37 (−5 to 54)% less than placebo (8.7 [5.8‐13.7] μIU/mL, P = .03); and at 120 min (10.2 [8.4‐12.2] μIU/mL) was 28 (−15 to 53)% less than placebo (14.9 [8.4‐24.8] μIU/mL, P = .02). There was minimal effect on glucose concentration. Insulin responses decreased toward baseline in ID horses after 7 days of treatment. Conclusion and Clinical Importance Sirolimus decreased the insulinemic response to glucose and warrants further investigation.

Abstract Background A glycemic challenge test is used for the diagnosis of insulin dysregulation (ID) in horses and ponies. Different forms of the test exist where the administrative route and dose of glucose vary, which makes interpretation of results challenging. Hypothesis/Objectives To evaluate the palatability of, and blood glucose and insulin responses to, carbohydrate pellets fed as an oral glucose test (OGT), and to establish the diagnostic threshold for ID when using the pellets. Animals University and privately‐owned horses and ponies (n = 157) comprised of 31 breeds and both sexes. Methods Multicenter cohort study. A custom‐produced glycemic pellet was offered for free intake at 0.5 g/kg BW soluble carbohydrate and serum insulin and blood glucose concentrations measured before and after (60, 120, and 180 minutes) the pellets were offered. Pellet acceptance and intake time (those that finished within 10 minutes) were determined to assess palatability. Results The pellets were palatable to 132/157 animals, and ponies found the pellets more (P = .004) palatable than horses. The median intake time (4 [3‐6] minutes) was positively correlated with acceptance grade (r = .51; P

Background: Sirolimus, a mechanistic target of rapamycin inhibitor, suppresses insulin production in other species and has therapeutic potential for hyperinsulinemia in horses. Hypothesis/Objective: Determine the pharmacokinetics (PKs) of sirolimus and evaluate its effect on insulin dynamics in healthy and insulin dysregulation (ID) horses. Animals: Eight Standardbred geldings. Methods: A PK study was performed followed by a placebo‐controlled, randomized, crossover study. Blood sirolimus concentrations were measured by liquid chromatography‐mass‐spectrometry. PK indices were estimated by fitting a 2‐compartment model using nonlinear least squares regression. An oral glucose test (OGT) was conducted before and 4, 24, 72, and 144 hours after administration of sirolimus or placebo. Effects of time, treatment and animal on blood glucose and insulin concentrations were analyzed using mixed‐effects linear regression. Sirolimus was then administered to 4 horses with dexamethasone‐induced ID and an OGT was performed at baseline, after ID induction and after 7 days of treatment. Results: Median (range) maximum sirolimus concentration was 277.0 (247.5‐316.06) ng/mL at 5 (5‐10) min and half‐life was 3552 (3248‐4767) min. Mean (range) oral bioavailability was 9.5 (6.8‐12.4)%. Sirolimus had a significant effect on insulin concentration 24 hours after a single dose: median (interquartile range) insulin at 60 min (5.0 [3.7‐7.0] μIU/mL) was 37 (−5 to 54)% less than placebo (8.7 [5.8‐13.7] μIU/mL, P =.03); and at 120 min (10.2 [8.4‐12.2] μIU/mL) was 28 (−15 to 53)% less than placebo (14.9 [8.4‐24.8] μIU/mL, P =.02). There was minimal effect on glucose concentration. Insulin responses decreased toward baseline in ID horses after 7 days of treatment. Conclusion and Clinical Importance: Sirolimus decreased the insulinemic response to glucose and warrants further investigation. [ABSTRACT FROM AUTHOR]

Background: A glycemic challenge test is used for the diagnosis of insulin dysregulation (ID) in horses and ponies. Different forms of the test exist where the administrative route and dose of glucose vary, which makes interpretation of results challenging. Hypothesis/Objectives: To evaluate the palatability of, and blood glucose and insulin responses to, carbohydrate pellets fed as an oral glucose test (OGT), and to establish the diagnostic threshold for ID when using the pellets. Animals: University and privately‐owned horses and ponies (n = 157) comprised of 31 breeds and both sexes. Methods: Multicenter cohort study. A custom‐produced glycemic pellet was offered for free intake at 0.5 g/kg BW soluble carbohydrate and serum insulin and blood glucose concentrations measured before and after (60, 120, and 180 minutes) the pellets were offered. Pellet acceptance and intake time (those that finished within 10 minutes) were determined to assess palatability. Results: The pellets were palatable to 132/157 animals, and ponies found the pellets more (P =.004) palatable than horses. The median intake time (4 [3‐6] minutes) was positively correlated with acceptance grade (r =.51; P <.0001). Consumption of the pellets elicited peak blood glucose (6.6 [5.8‐7.8] mmol/L) and serum insulin (40.5 [19‐99.8] μIU/mL) responses at 120 minutes. At 120 minutes the optimal cut‐off was 83 μIU/mL (95% CI: 70‐99 μIU/mL) for the IMMULITE 2000XPi assay. Conclusions and Clinical Importance: The pellets were palatable and a suitable, novel carbohydrate source for the OGT. [ABSTRACT FROM AUTHOR]

Background: Phenylbutazone is prescribed for laminitis-associated pain and decreases glucose and insulin responses to an oral glucose test (OGT) in horses with insulin dysregulation (ID)., Hypothesis/objectives: Investigate the effect of phenylbutazone administration on the enteroinsular axis in horses., Animals: Sixteen horses, including 7 with ID., Methods: Randomized cross-over study design, with horses assigned to treatment with phenylbutazone (4.4 mg/kg IV q24h) or placebo (5 mL 0.9% saline). On Day 9 of treatment, an OGT was conducted, followed by a 10-day washout period, administration of the alternative treatment, and repetition of the OGT. Glucose-dependent insulinotropic polypeptide (GIP), and active glucagon-like peptide 1 and 2 (aGLP-1 and GLP-2) concentrations were determined by ELISA. The effects of ID status and treatment on peptide concentrations were assessed using t tests and analyses of variance., Results: Horses with ID had significantly higher maximum GIP concentrations (Cmax) than controls (median, 279.1; interquartile range [IQR], 117.5-319.4 pg/mL vs median, 90.12; IQR, 74.62-116.5 pg/mL; P = .01), but no significant effect of ID was detected on aGLP-1 and GLP-2 concentrations. In horses with ID, phenylbutazone treatment significantly decreased GIP Cmax compared with placebo (168.1 ± 59.26 pg/mL vs 242.8 ± 121.8 pg/mL; P = .04), but no significant effect of phenylbutazone was detected on aGLP-1 and GLP-2 concentrations., Conclusion and Clinical Importance: Glucose-dependent insulinotropic polypeptide, aGLP-1 and GLP-2 do not mediate the decrease in glucose and insulin concentrations observed after phenylbutazone administration. Only GIP was repeatedly associated with ID status, calling into question the role of the enteroinsular axis in ID., (© 2024 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Abstract 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.

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

Background Supraphysiological insulin and incretin responses to a cereal‐based diet have been described in horses and ponies with insulin dysregulation (ID). However, the hormonal responses to grazing have not yet been described. Objectives To determine if there is a difference in the insulin and incretin responses to grazing pasture between insulin‐dysregulated and healthy ponies. Animals A cohort of 16 ponies comprising 5 with normal insulin regulation (NIR), 6 with moderate ID (MID), and 5 with severe ID (SID). Methods In this case‐control study, an oral glucose test (OGT) was used to determine the insulin responsiveness of each pony to PO carbohydrate before grazing pasture (4 hours) for 3 consecutive days. Serial blood samples collected during grazing were analyzed for glucose, insulin, glucose‐dependent insulinotropic peptide (GIP) and active glucagon‐like peptide‐1 (aGLP‐1), and compared among pony groups and day of pasture access. Results The area under the insulin curve when grazing increased with ID severity (P

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Supraphysiological insulin and incretin responses to a cereal‐based diet have been described in horses and ponies with insulin dysregulation (ID). However, the hormonal responses to grazing have not yet been described. Objectives: To determine if there is a difference in the insulin and incretin responses to grazing pasture between insulin‐dysregulated and healthy ponies. Animals A cohort of 16 ponies comprising 5 with normal insulin regulation (NIR), 6 with moderate ID (MID), and 5 with severe ID (SID). Methods: In this case‐control study, an oral glucose test (OGT) was used to determine the insulin responsiveness of each pony to PO carbohydrate before grazing pasture (4 hours) for 3 consecutive days. Serial blood samples collected during grazing were analyzed for glucose, insulin, glucose‐dependent insulinotropic peptide (GIP) and active glucagon‐like peptide‐1 (aGLP‐1), and compared among pony groups and day of pasture access. Results: The area under the insulin curve when grazing increased with ID severity (P < .03). The median (range) maximal insulin concentration was greater in the MID (72.5 [129] μIU/mL) and SID (255 [338.5] μIU/mL) groups, compared to the NIR (11.7 [24.9] μIU/mL) group (P < .03) and occurred within 2‐4 hours of grazing. Postprandial OGT insulin concentration was positively correlated with 2 hours post‐grazing insulin across all 3 grazing days (P ≤ .03). The aGLP‐1 and GIP concentrations increased in response to grazing but did not differ among groups. Conclusions and Clinical Importance: Grazing pasture provoked an increased insulin and incretin response in insulin‐dysregulated ponies within 4 hours of grazing. The pasture and OGT insulin concentrations were correlated. [ABSTRACT FROM AUTHOR]

Background: Metabolomics, the study of small-molecule metabolites, has increased understanding of human metabolic diseases, but has not been used to study equine metabolic syndrome (EMS). Objectives: (1) To examine the serum metabolome of Welsh Ponies with and without insulin dysregulation before and during an oral sugar test (OST). (2) To identify differences in metabolites in ponies with insulin dysregulation, obesity, or history of laminitis. Animals: Twenty Welsh Ponies (mean±SD; 13.8±9.0 years) classified as non-insulin dysregulated [CON] (n=10, insulin<30 mU/L) or insulin dysregulated [ID] (n=10, insulin>60 mU/L) at 75 minutes after administration of Karo syrup, obese (n=6) or nonobese (n514), and history of laminitis (n=9) or no history of laminitis (n=11). Methods: Case-control study. Metabolomic analysis was performed on serum obtained at 0 minutes (baseline) and 75 minutes during the OST. Data were analyzed with multivariable mixed linear models with significance set at P≤.05. Results: Metabolomic analysis of 646 metabolites (506 known) detected significant metabolite differences. At baseline, 55 metabolites (insulin response), 91 metabolites (obesity status), and 136 metabolites (laminitis history) were different. At 75 minutes, 51 metabolites (insulin response), 102 metabolites (obesity status), and 124 metabolites (laminitis history) were different. Conclusions and Clinical Importance: Use of metabolomics could have diagnostic utility for early detection of EMS and provide new knowledge regarding the pathophysiology of metabolic perturbations associated with this condition that might lead to improved clinical management. [ABSTRACT FROM AUTHOR]

The article presents two case studies of dogs with hyperinsulinemic hypoglycemia and bartonellosis. The first case involved a 6-month-old male castrated, 21-kilogram Weimaraner that developed seizures after surgical castration and umbilical hernia repair. While the second case involved a 9-month-old male 12.0-kilogram Pembroke Welsh Corgi was examined by the primary veterinarian after experiencing a 1-minute duration generalized seizure

The article presents a consensus statement on equine metabolic syndrome (EMS). Similar to the metabolic syndrome (MetS) in humans, the principal components of EMS include obesity, insulin resistance (IR) and laminitis in horses and ponies. To diagnose EMS, a complete history of the patient should be obtained, in addition to performing a physical examination, taking radiographs of the feet and conducting laboratory tests.

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., (© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

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., (© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)