Association of Season and Pasture Grazing with Blood Hormone and Metabolite Concentrations in Horses with Presumed Pituitary Pars Intermedia Dysfunction

Background: Pituitary pars intermedia dysfunction (PPID) is a risk factor for pasture‐associated laminitis, which follows a seasonal pattern. Hypothesis: Hormonal responses to season differ between PPID and unaffected horses. Animals: Seventeen horses aged 8–30 years (14 horses ≥ 20 years of age). Methods: Longitudinal observational study. Blood was collected monthly from August 2007 until July 2008 after pasture grazing and again after overnight stall confinement. Blood hormone and metabolite concentrations were measured and pasture grass samples were analyzed to determine carbohydrate content. Analysis of variance analysis for repeated measures was performed. Results: Mean ACTH concentrations varied significantly over time (P < .001), with higher concentrations detected in August, September, and October compared with November–April. Pasture × time effects were detected for glucose and insulin concentrations, with peaks observed in September. Horses were retrospectively allocated to PPID (n = 8) and control (n = 9) groups on the basis of plasma ACTH concentrations. Changes in insulin concentrations over time differed in the PPID group when compared with the control group. Insulin concentrations were positively correlated with grass carbohydrate composition. Conclusions and Clinical Importance: PPID did not affect the timing or duration of the seasonal increase in ACTH concentrations, but higher values were detected in affected horses. Insulin concentrations differed between groups, but hyperinsulinemia was rarely detected. Glucose and insulin concentrations peaked in September when horses were grazing on pasture, which could be relevant to the seasonal pattern of laminitis.     

Comparison of medical and surgical treatment for impaction of the small colon in horses: 84 cases (1986-1996)

OBJECTIVE: To characterize clinical findings and compare effects of treatment and outcome for horses treated medically or surgically for impaction of the small colon. DESIGN: Retrospective study. ANIMALS: 84 horses with impaction of the small colon. PROCEDURE: Medical records were reviewed for history, physical examination findings, laboratory values, treatment, response to treatment, complications, out-come, and necropsy findings. RESULTS: 47 horses were treated medically and 37 horses were treated surgically. Significant differences between groups were not identified for duration of clinical signs, physical examination findings, or laboratory values. Horses treated surgically were hospitalized longer than horses treated medically. Complications recorded during hospitalization included diarrhea, jugular thrombophlebitis, recurrent colic, fever, and laminitis. Salmonella organisms were isolated from 20 horses. Horses treated surgically were more likely to have signs of moderate abdominal pain, gross abdominal distention, and positive results for culture of Salmonella spp than horses treated medically. Follow-up information was available for 27 horses treated medically and 23 horses treated surgically. Twenty-four (72%) and 21 (75%) of the horses, respectively, survived and were being used for their intended purpose at least 1 year after treatment. CLINICAL IMPLICATIONS: Colitis may be a predisposing factor for impaction of the small colon in horses. Prognosis for horses treated surgically or medically is fair.     

Prevalence,risk factors and clinical signs predictive for equine pituitary pars intermedia dysfunction in aged horses

Reasons for performing study: Equine pituitary pars intermedia dysfunction (PPID) is an ageing‐related neurodegenerative disorder. The prevalence and risk factors for PPID using seasonally adjusted basal adrenocorticotropic hormone (ACTH) concentrations in aged horses have not been previously reported. Objectives: To determine the prevalence, risk factors and clinical signs predictive for PPID in a population of horses aged ≥15 years in Queensland, Australia. Methods: Owner‐reported data was obtained using a postal questionnaire distributed to an equestrian group. A subgroup of surveyed owners were visited and a veterinary physical examination performed on all horses aged ≥15 years. Blood samples were analysed for basal plasma alpha melanocyte‐stimulating hormone (α‐MSH) and ACTH concentrations, routine haematology and selected biochemistry. Aged horses with elevations above seasonally adjusted cut‐off values for basal plasma ACTH were considered positive for PPID. Positive horses were compared with their aged counterparts to determine risk factors and clinical signs associated with PPID. Results: Pituitary pars intermedia dysfunction was prevalent in aged horses (21.2%) despite owners infrequently reporting it as a known or diagnosed disease or disorder. Numerous clinical or historical signs were associated with an increased risk of PPID in the univariable model, but only age (odds ratio (OR) 1.18; 95% confidence interval (CI) 1.11–1.25, P<0.001) and owner‐reported history of hirsutism (OR 7.80; 95% CI 3.67–16.57, P<0.001) remained in the final multivariable model. There were no routine haematological or biochemical variables supportive of a diagnosis of PPID. Conclusions and potential relevance: Pituitary pars intermedia dysfunction occurs commonly in aged horses despite under‐recognition by owners. The increased risk of PPID with age supports that this is an ageing associated condition. Aged horses with clinical or historical signs consistent with PPID, especially owner‐reported hirsutism (delayed shedding and/or long hair coat), should be tested and appropriate treatment instituted.     

The effect of geographic location, breed, and pituitary dysfunction on seasonal adrenocorticotropin and α-melanocyte-stimulating hormone plasma concentrations in horses

Background: Plasma α‐melanocyte‐stimulating hormone (α‐MSH) and adrenocorticotropin (ACTH) concentrations in horses vary with season, confounding diagnostic testing for pituitary pars intermedia dysfunction (PPID). Hypothesis: The goals of this study were to determine whether seasonal variation in plasma α‐MSH and ACTH concentrations in horses is influenced by geographic location, breed, or PPID. Animals: Healthy light breed horses residing in Florida, Massachusetts, and Finland (n = 12 per group); healthy Morgan horses (n = 13); healthy ponies (n = 9) and horses with PPID (n = 8). Methods: Monthly plasma α‐MSH and ACTH concentrations were measured by radioimmunoassay. Nonlinear regression analysis was used to estimate the time of peak hormone concentrations. Mean hormone concentrations in fall and nonfall months were compared. Results: The fall peak plasma α‐MSH concentration occurred earlier in horses residing at more northern locations. Mean seasonal α‐MSH concentrations were similar in all healthy groups at all locations, but in the fall, plasma ACTH concentrations were higher in horses living in more southern locations. Plasma ACTH but not α‐MSH concentrations were higher in Morgan horses compared with light breed horses from the same location. Hormone concentrations of ponies did not differ from those of horses during either season. Concentrations of both hormones were high in the fall compared with the spring in horses with PPID. Conclusions and Clinical Importance: These findings suggest geographic location of residence and breed may affect the onset, amplitude, or both of the seasonal peak of pars intermedia (PI) hormones and should be considered when performing diagnostic testing for PPID. Horses with PPID maintain seasonal regulation of PI hormone output.     

Circannual variation in plasma adrenocorticotropic hormone concentrations in the UK in normal horses and ponies, and those with pituitary pars intermedia dysfunction

Reasons for performing study: Pituitary pars intermedia dysfunction (PPID) is a common endocrinopathy, frequently diagnosed via plasma adrenocorticotropic hormone (ACTH) concentrations. Seasonal variation in plasma ACTH concentrations has been described in normal horses prompting caution in diagnosing PPID at certain times of the year. The aims of this study were to determine appropriate reference intervals for equine plasma ACTH throughout the year; and to examine the circannual variation of plasma ACTH concentrations in PPID cases. Hypothesis: Plasma ACTH can be used as a test for PPID throughout the year with the use of appropriate reference intervals. Methods: Data for reference interval calculations were obtained from samples collected from inpatients of Liphook Equine Hospital (non‐PPID group, n = 156). Data from PPID cases (n = 941) were obtained from samples submitted to the Liphook Equine Hospital Laboratory from horses with a clinical suspicion of PPID found to have plasma ACTH concentrations greater than our upper reference interval for that time of year. Results: Upper limits for reference interval of plasma ACTH were 29 pg/ml between November and July and 47 pg/ml between August and October. Circannual variation in plasma ACTH occurred in both non‐PPID and PPID horses with the highest ACTH concentrations found between August and October in both groups (P<0.0001). The greatest difference between the 2 populations also occurred between August and October. Conclusions: Plasma ACTH can be used for the diagnosis and monitoring of PPID throughout the year with the use of appropriate reference intervals. These findings demonstrate an increase in pituitary gland secretory activity during the late summer and autumn in both normal and PPID cases.     

Correlation of Plasma Insulin Concentration with Laminitis Score in a Field Study of Equine Cushing's Disease and Equine Metabolic Syndrome

This study aimed to investigate endocrinologic test values and the response to treatment of two commonly encountered causes of endocrinopathic laminitis, equine Cushing's disease (ECD) and equine metabolic syndrome (EMS), in a veterinary practice setting. In particular, the study aimed to determine whether insulin concentration correlated to the severity of clinical laminitis in horses with EMS or ECD. Twenty-five horses were included in the study and assigned to one of three groups: ECD (n = 6), EMS (n = 10), and controls (n = 9). Blood samples were collected at an initial visit and then at regular intervals for the next 12 months. Plasma concentrations of adrenocorticotropin (ACTH), cortisol, and insulin and serum concentrations of glucose and total thyroxine (T4) were obtained. Horses with ECD had significantly higher plasma ACTH concentrations than EMS horses or controls. Horses with EMS and ECD both had significantly higher plasma insulin concentrations than control horses, which was correlated with the Obel grade of laminitis (r = 0.63). After treatment, there was a trend for a reduction in plasma ACTH concentration in horses with ECD. A program of diet and exercise for horses with EMS resulted in reductions in both plasma insulin concentrations and bodyweight, which was variable, depending on the individual. There was a significant correlation between the change in plasma insulin concentration and Obel grade of laminitis (r = 0.69). This study has highlighted the importance of baseline plasma insulin concentration as a potential indicator of the susceptibility of horses to laminitis and the response to a program of diet and exercise.     

Adrenocorticotropin concentration following administration of thyrotropin-releasing hormone in healthy horses and those with pituitary pars intermedia dysfunction and pituitary gland hyperplasia

OBJECTIVE: To compare the effect of thyrotropin-releasing hormone (TRH) administration on endogenous ACTH concentrations in healthy horses and those with pituitary pars inter-media hyperplasia and compare the test with the dexamethasone suppression test (DST). DESIGN: Prospective case series. ANIMALS: 15 horses with clinical signs of pituitary pars intermedia dysfunction (PPID), 4 horses with equivocal signs of PPID, and 29 horses without signs of PPID. PROCEDURES: ACTH concentrations prior to and after administration of TRH were measured 61 times in 48 horses. Results of the DST (cortisol response) were compared with those of the TRH test in 29 horses. Thirty-three horses (24 with no clinical signs of PPID, 5 with clinical signs of PPID, and 4 with equivocal clinical signs of PPID) were euthanized and necropsied and their pituitary glands evaluated. RESULTS: ACTH concentrations increased in all horses, but magnitude and duration of increase were significantly higher in horses with PPID. Endogenous ACTH concentrations were influenced by season. The ACTH baseline concentrations and response to TRH were not correlated with results of the DST. Results of DST were abnormal only in clinically abnormal horses or those with pars intermedia hyperplasia, but were within reference range in 17 of 26 tests in these horses. CONCLUSIONS AND CLINICAL RELEVANCE: The ACTH response to TRH is a useful test for diagnosis of pituitary gland hyperplasia, particularly in horses in which baseline ACTH concentrations are within reference range. The DST was specific but not sensitive and was inconsistent for individuals, and results often did not agree with the TRH test response.     

Evaluation of basal plasma α‐melanocyte‐stimulating hormone and adrenocorticotrophic hormone concentrations for the diagnosis of pituitary pars intermedia dysfunction from a population of aged horses

Reasons for performing study: The sensitivity and specificity of basal plasma α‐melanocyte‐stimulating hormone (α‐MSH) and adrenocorticotrophic hormone (ACTH) for the diagnosis of pituitary pars intermedia dysfunction (PPID) has not been evaluated in a population‐based study. Objectives: To evaluate basal plasma α‐MSH and ACTH concentrations for the diagnosis of PPID in a population of horses aged ≥15 years. Methods: Owner‐reported data were obtained using a postal questionnaire distributed to an equestrian group. A subgroup of surveyed owners was visited and veterinary examination performed on horses aged ≥15 years. Blood samples were analysed for plasma α‐MSH and ACTH concentrations. Seasonally adjusted cut‐off values for α‐MSH and ACTH concentrations for the diagnosis of PPID were obtained using Youden index values against a clinical gold standard diagnosis (hirsutism plus 3 or more clinical signs of PPID). Results: α‐melanocyte‐stimulating hormone and ACTH were highly correlated with each other and with clinical and historical indicators of PPID. The increase in both α‐MSH and ACTH with increasing numbers of clinical signs in affected horses supports a spectrum of disease. Both variables were affected by season, with derived cut‐off values being higher in autumn compared with other seasons. Sensitivity and specificity were moderate and good in nonautumn seasons (59 and 93%, respectively) for α‐MSH using a cut‐off of 52.0 pmol/l. Sensitivity and specificity were good in nonautumn seasons (80 and 83%, respectively) for ACTH using a cut‐off of 29.7 pg/ml. For both α‐MSH and ACTH, sensitivity and specificity were close to 100% for samples obtained during the autumn period. Conclusions and potential relevance: Basal plasma α‐MSH and ACTH had moderate‐to‐good sensitivity and specificity for the diagnosis of PPID, which improved substantially during the autumn period, suggesting this may be the ideal time to test. Further studies to develop seasonally adjusted reference intervals for different geographical locations are warranted.     

Cytokine dysregulation in aged horses and horses with pituitary pars intermedia dysfunction

BACKGROUND: Equine pituitary pars intermedia dysfunction (PPID) is the result of a loss of dopaminergic inhibition of the pars intermedia secondary to neurodegeneration of periventricular hypothalamic neurons. The pathologic events contributing to development of neurodegeneration or clinical signs in equids with PPID are unknown. Chronic inflammation may contribute to initiation or progression of PPID. HYPOTHESIS: Horses with PPID have a distinct systemic cytokine profile compared with that of normal adult or aged horses. The cytokine profile of healthy aged horses differs from that of adult horses. ANIMALS: Aged horses with PPID, healthy aged-matched controls, and adult controls (n = 14 per group). METHODS: Total leukocyte cytokine expression was determined by quantitative polymerase chain reaction (PCR), and tumor necrosis factor (TNF)-alpha plasma concentration was determined by enzyme-linked immunosorbent assay (ELISA). Peripheral blood mononuclear cell (PBMC) TNF-alpha response after endotoxin (lipopolysaccharide [LPS]) treatment was assessed by ELISA. RESULTS: Aged healthy horses had increased expression of interleukin (IL)-6, IL-8, and interferon-gamma as well as PBMC TNF-alpha release after LPS stimulation compared with healthy adult horses. In contrast, aged horses with PPID had increased IL-8 expression, but expression of other cytokines was similar to that of healthy adult horses, not age-matched controls. CONCLUSIONS AND CLINICAL IMPORTANCE: Aged horses show evidence of a proinflammatory state that may contribute to development of age-associated diseases. Horses with PPID have increased expression of IL-8, which may influence the ability of horses with PPID to respond to bacterial pathogens. The general decrease in proinflammatory cytokine expression observed in horses with PPID may be the outcome of high plasma concentrations of anti-inflammatory hormones.     

Pharmacokinetic and pharmacodynamic properties of pergolide mesylate following long‐term administration to horses with pituitary pars intermedia dysfunction

The objective of this study was to gain an understanding of the pharmacokinetic and pharmacodynamic properties of pergolide in horses with PPID after of long‐term oral administration. Six horses with confirmed PPID were treated with pergolide (Prascend^®) at 1 mg/horse po q24 h for 2 months, followed by 2 mg/horse po q24 h for 4 months. Following the last dose, plasma samples were collected for measurement of pergolide using an LC/MS/MS method and ACTH measurement using a chemiluminescent immunoassay. Noncompartmental and compartmental pharmacokinetic analyses were performed, as well as pharmacodynamic assessment of the effect of plasma pergolide concentrations on plasma ACTH concentrations. Pergolide effectively decreased plasma ACTH concentration in aged horses with PPID, with similar pharmacokinetic properties as reported in young horses, including an approximate terminal half‐life of 24 h. Plasma ACTH concentration increased by 50% in 3/6 horses at 2 days and 6/6 horses 10 days after discontinuing drug administration. Pergolide was quantified in all horses at 2 days and in none at 10 days after last dose. In summary, after discontinuing pergolide treatment, plasma ACTH concentration increased while pergolide was still quantifiable in some horses. Once‐daily dosing of pergolide is likely appropriate in most horses with PPID for regulating the plasma ACTH concentration.     

Correlation of pituitary histomorphometry with adrenocorticotrophic hormone response to domperidone administration in the diagnosis of equine pituitary pars intermedia dysfunction

Functional evaluation of the pars intermedia (PI) is required for the early diagnosis of equine pituitary PI dysfunction (PPID), yet most assays target the hypothalamic-pituitary-adrenal axis, which regulates the pars anterior. In contrast, the PI is regulated by dopaminergic tone from hypothalamic neurons. Loss of dopaminergic inhibition is hypothesized to cause the PI hypertrophy and hyperplasia that result in the clinical manifestations of PPID. Domperidone, a dopamine receptor antagonist, should exacerbate the loss of dopaminergic inhibition in horses with PPID and increase the release of endogenous adrenocorticotrophic hormone (eACTH) by PI melanotrophs. To test this, plasma eACTH concentration was determined in horses with or without clinical signs of PPID at 0, 4, and 8 hours after oral administration of 3.3 mg domperidone/kg. Pituitary glands were evaluated postmortem by histologic grading and morphometry. In the 33 horses, median age, plasma ACTH concentration 8 hours after domperidone, and PI area in median sagittal sections were associated with histologic grade as follows: pituitary grade 1 (normal), n = 3, 7.5 years, 20.0 pg/ml, 0.16 cm(2); grade 2 (focal hypertrophy or hyperplasia), n = 9, 14.5 years, 27.1 pg/ml, 0.27 cm(2); grade 3 (diffuse adenomatous hyperplasia), n = 5, 21.0 years, 64.4 pg/ml, 0.48 cm(2); grade 4 (microadenomas), n = 12, 23.3 years, 128.0 pg/ml, 0.87 cm(2); grade 5 (adenoma), n = 4, 24.9 years, 720.5 pg/ml, 2.1 cm(2). Results suggest that horses with pituitary histologic grade > or =3 respond to domperidone with increased plasma ACTH concentration.     

Results of intradermal tests in horses without atopy and horses with chronic obstructive pulmonary disease

OBJECTIVE: To compare results of intradermal tests (IDT), conducted using environmental allergens, in horses without atopy and horses with chronic obstructive pulmonary disease (COPD). ANIMALS: 38 horses (22 horses without atopy and 16 horses with COPD). PROCEDURE: All horses were examined (physical examination, hematologic examination, serum biochemical analyses, examination of bronchoalveolar lavage fluid). An IDT was conducted, using a full panel of 73 allergens consisting of grasses, weeds, trees, molds, and insects. Results of the IDT were evaluated 30 minutes and 4, 6, and 24 hours after injection of allergens. Horses without atopy were euthanatized, and gross and histologic changes of lung parenchyma were assessed. RESULTS: Horses without atopy had a greater number of positive immediate and late-phase reactions than did horses with COPD. Horses with COPD did not have a significantly greater number of positive reactions than horses without atopy at any time period for any allergen group (grasses, weeds, trees, molds, and insects). CONCLUSIONS AND CLINICAL RELEVANCE: Positive results of IDT document allergen-specific hypersensitivity but do not necessarily distinguish clinically relevant reactions from subclinical reactivity in horses with COPD. Interpreting the clinical relevance of results of IDT requires a thorough knowledge of the medical history, physical examination findings, and environment of each animal.     

Pericarditis in horses: six cases (1982-1986)

Records of 6 horses with pericarditis were reviewed. Septic pericarditis was suspected in all horses, based on historic and clinical findings. In horses 1, 2, and 4, cytologic examination of the pericardial effusion revealed acute inflammation with severe neutrophil degeneration. In horses 3 and 5, cytologic examination of pericardial fluid revealed subacute inflammation with degenerated neutrophils, and in horse 6, chronic active inflammation, with well preserved neutrophils. In horses 1 and 3, bacteria were identified on cytologic examination of pericardial fluid. Results of microbiologic cultures of pericardial fluid were positive in horse 3. All horses were treated with broad-spectrum antibiotics. An indwelling pericardial catheter was used to lavage and directly administer antibiotics into the pericardial sac. Horses 1, 4, 5, and 6 survived, horse 2 died of unrelated causes, and horse 3 was euthanatized at the owner's request. Surviving horses returned to athletic performance.     

Comparison of Insulin and Glucose Metabolism in Horses with Pituitary Pars Intermedia Dysfunction Treated Versus Not Treated with Pergolide

Equine pituitary pars intermedia dysfunction (PPID) is known to alter glucose/insulin metabolism. This study evaluated changes in parameters relating to glucose/insulin metabolism and determined whether there is a difference between pergolide-treated and untreated animals. We hypothesized that glucose/insulin dynamics in PPID horses receiving pergolide would be different than those in untreated horses. A total of 38 horses with diagnoses of PPID were included in the study (average age: 24 years). A total of 25 horses were untreated; 13 horses were treated with pergolide (>3 months). Parameters relating to glucose/insulin metabolism were determined in all horses, as follows: adrenocorticotropin-releasing hormone (ACTH), insulin, fructosamine, triglyceride, glucose, modified insulin-to-glucose ratio (MIRG), and reciprocal of the square root of insulin (RISQI). A combined glucose-insulin test (CGIT) was performed in 23 horses as not all owners agreed to the testing. Treated animals showed a tendency to have lower ACTH, but results were not significant. All animals had fructosamine levels exceeding reference values (mean value 314 ± 32 μmol/L; reference range: <280 μmol/L). There were no statistically significant differences between insulin, glucose, ACTH, triglycerides concentrations, RISQI/MIRG calculations, and CGIT results of pergolide-treated PPID and those of untreated horses. Five horses (13.2%) had combined hyperglycemia/hyperinsulinemia, whereas 7 horses (18.4%) displayed hyperglycemia, and 3 horses (7.9%) showed hyperinsulinemia alone. Forty percent of the horses with altered glucose/insulin metabolism were treated with pergolide. Based on RISQI and MIRG calculations, 19 animals displayed changes in glucose/insulin metabolism. Fourteen of twenty-three horses (61%) showed signs of insulin resistance in CGIT results. In conclusion, PPID horses frequently show alterations in glucose/insulin metabolism, but no significant differences were found between treated and untreated animals. Changes in insulin/glucose dynamics may not be a useful indicator of response to pergolide treatment.     

Assessment of clinical characteristics,management practices,and activities of geriatric horses

OBJECTIVE: To describe the demographic and clinical characteristics, management practices, and owner perception of a population of geriatric horses, and to compare these data with findings in a group of younger horses. DESIGN: Original study. ANIMALS: 218 horses. PROCEDURE: Data were collected via a survey tool from owners of 165 horses that were > or = 20 years of age and 53 horses that were < 20 years of age. RESULTS: Compared with young horses, the geriatric group included a significantly greater number of ponies; geriatric horses were also more likely to have a history of colic, dental disease, tumors, lameness, and pituitary disease, but not laminitis, diarrhea, allergies, respiratory tract disease, thyroid disease, or fractures. Horses that had participated in Western equestrian disciplines were more likely to have a history of lameness. Among old horses, those with pituitary dysfunction were more likely to have a history of laminitis than those without pituitary dysfunction. Geriatric horses were more likely to have long hair and shedding abnormalities than were younger horses. Owners perceived their horses as old at approximately 22 years of age. In horses older than 16.5 years of age, age was a negative factor in the purchase of horses. CONCLUSIONS AND CLINICAL RELEVANCE: Geriatric and young horses share some similar health problems, but old horses have distinct health problems and veterinary medical requirements. The management and athletic history of horses may influence health as they age.     

Treatment with pergolide or cyproheptadine of pituitary pars intermedia dysfunction (equine Cushing's disease)

Medical records of 27 horses (including 13 ponies) treated with pergolide or cyproheptadine for pituitary pars intermedia dysfunction were reviewed to determine the effect of treatment on plasma ACTH, insulin, and glucose concentrations and clinical signs. Prior to treatment, the most common clinical signs were laminitis, hirsutism, and abnormal body fat distribution. The median pergolide dose was 3.0 microg/kg p.o. q24h (range, 1.7-5.5 microg/kg). All horses treated with cyproheptadine were given 0.25 mg/kg p.o. q24h. After pergolide treatment, ACTH concentrations (n = 20; median = 30.4 pg/ml; range, 4.2-173) were significantly lower (P < .01) than those in horses treated with cyproheptadine (n = 7; median = 141.0 pg/ml: range, 10-1,230). Among horses treated with pergolide, there was a correlation between ACTH concentration after treatment and the duration of treatment (P < .001) and pergolide dose (P = .04). Significantly (P = .02) more owners of horses treated with pergolide (85%, 17/20) reported an improvement in clinical signs compared to owners of horses treated with cyproheptadine (28%, 2/7).     

Suspensory ligament degeneration associated with pituitary pars intermedia dysfunction in horses

In older horses, pituitary pars intermedia dysfunction (PPID) and suspensory ligament (SL) degeneration are common. The aim of the present study was to identify histopathological changes in the SL in horses with PPID. SLs of four horses with clinical signs of PPID (17–26 years of age) were compared with SLs from four old horses (18–31 years of age) and three young horses (4–9 years of age). In horses with PPID, there was reduced longitudinal arrangement of collagen fibres in SLs, along with inclusions of cartilage, extracellular matrix and haemorrhage, as well as significant proteoglycan accumulations between SL fibres. These changes are similar to the degeneration of connective tissues in Peruvian Paso horses with SL degeneration and in humans with Cushing's disease or after long term high dose corticosteroid treatments. These findings indicate an association between degeneration of the SL and PPID.     

Equine laminitis caused by distal displacement of the distal phalanx: 12 cases (1976-1985)

Clinical data from 12 cases of equine laminitis characterized by distal displacement of the distal phalanx (P3) were reviewed. Clinical features of horses that survived the syndrome were compared with the nonsurvivors to obtain prognostic indicators. Animals affected included 8 Quarter Horses, 2 Welsh ponies, 1 Thoroughbred, and 1 Arabian. Eight of the animals were females (67%), 2 were stallions, and 2 were geldings. The mean age of affected animals was 8.6 years (2 to 14 years), and the mean body weight was 442 kg. The survivors weighed less than the nonsurvivors (384 kg vs 473 kg, respectively), suggesting that body weight may be of prognostic value for horses affected with distal displacement of P3. Ten of the 12 animals (83%) were admitted because of a disorder other than laminitis, but subsequently developed laminitis during the treatment period. All affected animals had clinical evidence of endotoxemia and/or sepsis before the onset of laminitis. Cavitation or depression of the dorsal coronary band was detected in all animals and was the most reliable clinical indicator of distal displacement of P3. Five horses had fluid (blood or serum) ooze from their coronary bands and 2 of these sloughed one or more of their hooves. Necropsy findings of the 8 horses that were euthanatized included severe hemorrhagic, congested laminae and complete detachment of P3 from the hoof wall. Histologic examination of affected laminae revealed vascular thrombosis and multifocal areas of hemorrhage and necrosis. Radiography failed to reveal distal displacement of P3 in 8 animals, but the remaining 4 animals had an accentuation of the dorsal proximal hoof wall and cavitation of the coronary band visible on lateral radiographs.     

Agreement in histologic assessments of the pituitary pars intermedia in aged horses

OBJECTIVE: To evaluate concordance among veterinary pathologists in the assessment of histologic findings in the pars intermedia of pituitary gland sections from aged horses with mild signs suggestive of pituitary pars intermedia dysfunction (PPID). Sample Population-10 pituitary glands from aged horses. PROCEDURE: 7 pathologists were provided with signalment, clinical signs, and a single H&E-stained pituitary gland section from 10 aged horses with mild signs suggestive of PPID. Pathologists described histologic findings for each section and stated whether findings were consistent with PPID. Agreement among pathologists and with antemortem diagnostic test results was calculated. RESULTS: Overall, only fair agreement was found among the pathologists as to which horses had histologic findings consistent with disease (mean +/- SE kappa value, 0.34 +/- 0.069). Interpretation of individual sections varied, with minimal agreement (4 or 5/7 pathologists) for 5 of 10 sections evaluated. Postmortem assessment was in agreement with an antemortem endocrine diagnostic test result 79% of the time. CONCLUSIONS AND CLINICAL RELEVANCE: Validation of antemortem diagnostic testing for PPID in horses often relies on the results of postmortem histologic evaluation. The lack of consensus in histologic interpretation of pituitary glands from aged horses with mild clinical signs in our study indicates that postmortem histologic evaluation of pituitary glands is an inappropriate standard in validation of antemortem diagnostic tests for detection of early PPID. Caution should be used when interpreting diagnostic test results in horses in which early PPID is suspected.