How To Diagnose And Treat Equine Cushings Disease

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1 Equine Endocrine Disease: Cushings and Equine Metabolic Syndrome Dr. Martin Furr Dip ACVIM, PhD Adelaide C Riggs Professor of Medicine Acknowledgements to Dr Scott Pleasant for some slides

2 Endocrine Disease Endocrine system Interacting system of organs that produce hormones regulating many body functions Pituitary, thyroid, adrenal glands, etc. 2 most common equine conditions Cushings disease Equine Metabolic Syndrome/Insulin resistance syndrome

3 Equine Cushings Disease A syndrome in which there is excessive secretion of the hormones ACTH (pituitary) and cortisol (adrenal gland) aka equine cushings syndrome, pituitary adenoma, pars intermedia adenoma, Most properly referred to as pituitary pars intermedia dysfunction (PPID) A common clinical syndrome in older horses 15-30% of horses > 15 years No gender bias, ponies and Morgans more likely

4 Equine Pituitary Gland

5 Disease mechanism Pituitary gland enlarges (pituitary adenoma) Too much ACTH hormone is released into the bloodstream Excess cortisol is secreted from the adrenal glands in response to the ACTH Feedback inhibition of ACTH by cortisol is blocked Clinical signs result from excess cortisol and other as yet unidentified hormonal products

6 Long shaggy hair coat (hirsutism) Laminitis Excessive water consumption and urination (polydypsia/polyuria) Weight loss and pot belly Recurrent infections, blindness, skin infections, lethargy, hyperhydrosis, infertility Clinical Signs

7 Diagnosis Characteristic clinical signs In advanced cases only! Characteristic changes in routine labwork (not always present!): High white blood cell count Anemia High resting glucose concentration 45% in one study, 95% in another Glucose in urine

8 Specific Diagnostic Tests Resting cortisol concentrations Large horse to horse variation Day to day variation Not all horses with PPID have high cortisols Cortisol is influenced by many different things Not the best method

9 Specific Diagnostic Tests Resting ACTH concentrations Day to day, horse to horse and season to season variation Better diagnostic value than cortisol 91% accurate for horses 80% accurate for ponies

10 Serum Cortisol (ng/ml) Specific Diagnostic Tests Dexamethasone suppression test Baseline blood cortisol Suppress with dexamethasone Assay blood cortisol again Normal cortisol drops PPID cortisol does not drop 20% error rate(?) Multiple samples, expense :00 3:30 4:00 24:00:00 Time Post Dexamethasone Normal Abnormal 1 Abnormal 2

11 Specific Diagnostic Tests Combined Dexamethasone suppression/trh stimulation test Measure cortisol: at baseline after suppression after stimulation 85% accuracy Multiple blood samples, expense

12 Treatment/Management PPID is NOT curable- but it is manageable Combination of management and drugs Good quality feed/nutritional management Dental care Foot care Clip long hair in non-shedders

13 Drugs for PPID Pergolide.5 mg twice per day PO Monitor ACTH and clinical signs every 6 weeks Increase by.5 mg if not controlled Cost- 1-2$/day

14 Drugs for PPID Ciproheptadine.25 mg/kg per day Monitor ACTH at 6 weeks No response- increase the dose to twice per day Monitor again Cost 1$/day

15 Equine Metabolic Syndrome A syndrome of insulin resistance associated with obesity and pasture associated laminitis

16 Insulin and Glucose Insulin Regulates blood glucose As glucose goes up- insulin goes up in response Insulin stimulates cellular uptake of the glucose Blood glucose goes down as a result

17 Insulin Resistance/Hyperinsulinemia insulin resistance (IR): inability of insulin to result in an appropriate decrease in blood glucose hyperinsulinemia (high blood levels of insulin): compensatory response which may maintain a proper insulin mediated responses (is an indicator of IR)

18 Equine Metabolic Syndrome Clinical Signs Obesity and regional adiposity Observation, body scoring, scales, or weight tapes Cresty neck Insulin resistance Subclinical or chronic laminitis Observation of founder rings Clinical laminitis Radiographs of feet (rotation)

19 Diagnosis of Insulin Resistance Resting blood insulin concentrations Resting blood glucose concentrations Tests should be done after 6 hours of fed deprivation Glucose Insulin Interpretation normal normal Normal normal high Compensated IR high high Uncompensated IR

20 Combined glucoseinsulin test More sensitive than resting measurements Baseline measurement Glucose and insulin given Follow-up blood samples Insulin Resistance Diagnosis

21 Equine Obesity and Insulin Resistance Incidence? What is the evidence for a connection?

22 Equine Obesity United States Department of Agriculture has estimated that approximately 5% of the U.S. horse population is overweight or obese this estimate was based on an owner survey (USDA NAHMS 1998)

23 Virginia Tech Equine Obesity Study Study Objectives determine the prevalence of obesity in a sub-population of mature horses in Virginia. determine the prevalence of hyperinsulinemia (HI) in these horses examine the relationships between obesity and hyperinsulinemia (Geor, Pleasant, Thatcher et al VHIB, VMRCVM, DAPS)

24 VT Obesity Study Study Methods 300 horses, between 4-20 years of age (randomly selected from a master list of approximately 1000 horses) Summer 2006 (60 days) history gathered, body condition evaluated (2 evaluators), blood collected (horses evaluated and blood samples collected between 6-11 AM, before concentrate meals)

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26 Body Condition Score 1 Poor Animal extremely emaciated; spinous processes, ribs, tailhead, tuber coxae, and ischii projecting prominently; bone structure of withers, shoulders, and neck easily noticeable; no fatty tissue can be felt

27 Body Condition Score 5 Moderate Condition Back is flat (no crease or ridge); ribs not visually distinguishable but easily felt; fat around tailhead beginning to feel spongy; withers appear rounded over spinous processes; shoulders and neck blend smoothly into body

28 Body Condition Score 9 Extremely Fat Obvious crease down back; patchy fat appearing over ribs; bulging fat around tailhead, along withers, behind shoulders, and along neck; fat along with inner thighs may rub together; flank filled with fat

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30 Number of Results Levels of Exercise in the Study Population % 23 % 15 % 3 % None Light Moderate Intense Exercise Regimen Light: 1-3 hrs per week Moderate: 3-5 hrs per week Intense: > 5 hrs per week

31 Number of Horses Results Distribution of Horses by Amount of Concentrate/Grain Fed Per Day % % % 7 % 4 % 0 None >0 but < >8 Concentrate Fed (lbs/day)

32 Number of Horses Results % Distribution of Body Condition Categories 47 % 32 % 19 % 0 Under Condition Optimal Condition Over Condition Obese Condition Body Condtion Under Condition = BCS < 4 Optimal Condition = BCS 4-6 Over Condition = BCS Obese Condition = BCS 7.5-9

33 Geometric mean of Insulin concn + 1 geometric SD (uiu/ml) Results Insulin Concentration versus Body Condition Under Conditioned Optimal Conditioned Over Weight Obese Body Condition Under Condition = BCS < 4 Optimal Condition = BCS 4-6 Over Condition = BCS Obese Condition = BCS 7.5-9

34 Number of Horses Results Hyperinsulinemia Within Each Body Condition Below Baseline Hyperinsulinemic % 32 % 0 % 1.4% Under Condition Optimal Condition Over Condition Obese Condition Body Condition Under Condition = BCS < 4 Optimal Condition = BCS 4-6 Over Condition = BCS Obese Condition = BCS 7.5-9

35 Summary prevalence of over conditioned/obesity (BCS 6.5-9) of the study horse population was 51% prevalence of obesity (BCS 8-9) of the study horse population was 19%

36 Summary 1.4% of optimally conditioned or underweight horses were hyperinsulemic 10% of overconditioned horses were hyperinsulinemic 32% of obese horses were hyperinsulinemic

37 Why do Horses Become Obese?

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39 % of Required Nutrients Supplied (unrestricted pasture) 300% 250% 200% 150% 285% Pasture 100% 50% 128% 136% 136% 0% DE CP Ca P

40 Pasture Associated Laminitis Why?

41 Pasture Associated Laminitis Nonstructural Carbohydrate (NSC) Induced Laminitis (starch or fructan: mechanism of) excess nonstructural carbohydrate enters the large intestine lactic acid bacteria population explosion acid kills off other resident bacteria and damages the intestinal lining

42 Pasture Associated Laminitis NSC Induced Laminitis (mechanism of) substances enter the blood, travel to the foot causes lamellar inflammation clinical signs seen depend on the amount of laminar damage

43 Pasture Associated Laminitis (it s a little lot more complicated than that!) Risk Factors: high NSC intake from pasture (rarely causes by itself) generalized obesity and regional adiposity insulin resistance/hyperinsulinemia

44 Obesity/Regional Adiposity Increased Risk for PAL (mechanisms of?) increased load on lamellar tissues production of a state of chronic inflammation altered vascular responses induction of IR/hyperinsulinemia

45 Insulin Resistance/HyperInsulinemia Increased Risk for PAL (mechanisms of?) epidermal cell dysfunction pro-inflammatory effects vascular dysfunction laminar deterioration and laminitis

46 Treatment of EMS If you prevent obesity..you will vastly reduce (if not eliminate) IR/hyperinsulinemia and Pasture Associated Laminitis

47 Prevention of Obesity Feed appropriately for the body weight and amount of exercise regularly monitor body condition (monthly) Weight tapes, scales, body measurements, condition score provide regular exercise (energy requirements for light work is 1.25 x maintenance)

48 Body Measurements Neck Crest Adiposity Cresty Neck Neck circumference (inches) midway between the poll and the withers Height at withers (inches) Neck circumference/height ratio horse > 0.63 = cresty ponies > 0.68 = cresty

49 Body Weight Estimation Weight (in lbs) = girth (inches) x girth (inches) x body length (inches) divided by 330 Example: Girth 73 inches, body length 67 inches 73 x 73 x 67/ 330 = /330= 1082 lbs

50 Treatment of Obesity feed an average quality hay in an amount equivalent to 2% of desired body condition/weight Weigh the hay, concentrate not usually necessary unless in moderate to heavy work, or lactating mares limit grazing, use grazing muzzles, dry lots, etc exercise As permitted by laminitis or other conditions Even a little helps!

51 Grazing Guidelines Limit grazing of lush pasture (restriction or grazing muzzles) Spring, early summer After a bloom After a frost Avoid flowering grasses (high sugar) Graze in early morning before 10 am Avoid overgrazing (more NSC in lower stems) Prefer native to improved pastures

52 How to adjust diet? Treatment of Obesity: Example (starting weight = 1200#/starting BCS = 9) 1200# [(9 5) x 50#] = 1000# Current BW Current BCS Desired BCS Estimated Optimum BW *feed 20# of average quality hay daily

53 Treatment Metformin (Glucophage ) Improves insulin sensitivity at the tissue level Conflicting data at present Thyroid hormone supplementation Widely advocated, conflicting effectiveness Special diets and supplements Magnesium, chromium, zinc, clenbuterol, cinnamon, ginger root, grapeseed extract, antioxidants

54 4 months later

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