Equine Metabolic Syndrome (EMS)

Equine Metabolic Syndrome is a widespread endocrine disorder characterized by obesity or regional adiposity, insulin dysregulation, and an increased predisposition to laminitis. This condition represents one of the most significant metabolic health challenges facing the modern horse population, with prevalence estimates suggesting that up to thirty percent of some equine populations may be affected. The central feature of EMS is insulin dysregulation, which may manifest as fasting hyperinsulinemia, an exaggerated and prolonged insulin response to oral carbohydrates, or insulin resistance at the tissue level. This metabolic dysfunction creates a persistent state of risk for endocrinopathic laminitis, a painful and potentially devastating condition of the hooves.

Equine Metabolic Syndrome affects horses and ponies of all breeds but is particularly prevalent in certain populations. Native pony breeds including Welsh, Shetland, and British native ponies show very high rates of the condition. Breeds characterized as easy keepers, meaning they maintain or gain weight readily on minimal feed, are at elevated risk. This includes Morgans, Paso Finos, Peruvian Pasos, Quarter Horses, Arabians, and their crosses. Draft breeds and warmbloods can also be affected, particularly when overfed relative to their exercise level. The condition is less common in Thoroughbreds and other breeds that tend to be hard keepers, though no breed is completely exempt.

The impact of EMS on affected horses is substantial and often lifelong. The most serious consequence is laminitis, which can cause acute and severe lameness, permanent structural damage to the hooves, and in severe cases necessitates euthanasia. Even without clinical laminitis episodes, the chronic metabolic stress of insulin dysregulation may contribute to other health problems. Horses with EMS typically require significant management modifications including dietary restriction, increased exercise, and often permanent limitations on pasture access. The quality of life for well-managed EMS horses can be excellent, but the condition requires ongoing commitment from owners and represents a significant lifestyle change from typical horse keeping.

Equine Metabolic Syndrome is manageable but not curable in the traditional sense, as the underlying metabolic tendencies persist throughout the horse's life. Management success depends on consistent dietary control, appropriate exercise, weight management, and vigilant monitoring for signs of laminitis. Early detection allows intervention before serious complications develop, and horses identified as at-risk can often be managed preventively. Medical therapies can assist in managing insulin dysregulation when lifestyle modifications alone are insufficient. With proper management, many horses with EMS live comfortable, useful lives, but the condition requires acceptance that affected horses have special needs that cannot be ignored.

The primary causes of Equine Metabolic Syndrome involve a complex interplay between genetic predisposition and environmental factors, particularly nutrition and exercise. At its core, EMS represents a maladaptive response to modern management conditions in horses that evolved to thrive on sparse, low-quality forage with significant daily movement. When these horses are fed abundant, high-calorie diets and kept in situations with limited exercise, their efficient metabolisms lead to obesity and metabolic dysfunction. The condition is fundamentally a mismatch between genetic makeup and modern management, though the exact genetic variants responsible have not been fully characterized.

Genetic and breed predisposition to EMS is well established, with certain breeds and family lines showing markedly higher susceptibility. The thrifty genotype hypothesis suggests that these horses carry genetic adaptations for surviving in harsh environments with limited food, enabling them to extract maximum nutrition from poor-quality forage and store energy efficiently as fat. While advantageous for survival in their native habitats, these same adaptations become problematic when abundant food is available. Studies have demonstrated that pony breeds can develop insulin resistance and obesity on diets that would be maintenance or even inadequate for other horses. The heritable nature of EMS is supported by observations of familial clustering.

Environmental and management factors are essential contributors to the expression of EMS in genetically predisposed horses. Overfeeding is the single most important environmental factor, with excess caloric intake driving weight gain and metabolic dysfunction. Diets high in nonstructural carbohydrates, particularly sugars and starches from grain-based feeds and rich pastures, directly challenge insulin regulation and worsen insulin dysregulation. Inadequate exercise reduces glucose utilization and insulin sensitivity, compounding the effects of overfeeding. The modern tendency to keep horses in situations with limited movement and abundant food creates perfect conditions for EMS to develop in susceptible individuals.

Risk factors for developing Equine Metabolic Syndrome include breed and genetic background, diet composition and quantity, exercise level, age, and existing body condition. Easy-keeper breeds are at inherently higher risk. Horses fed grain-based concentrates, sweet feeds, or allowed unlimited access to lush pastures face greater metabolic challenges. Sedentary horses that spend most of their time in stalls or small paddocks without regular exercise have higher risk than those in consistent work. Middle-aged horses seem most commonly diagnosed, though the condition can develop at any age. Horses that are already overweight or have regional fat deposits are demonstrating the metabolic dysfunction characteristic of EMS.

The pathophysiology of EMS involves several interconnected mechanisms centered on insulin dysregulation. Adipose tissue, particularly the metabolically active regional fat deposits in the crest, shoulders, and tailhead, produces inflammatory cytokines and hormones that promote insulin resistance at the tissue level. As tissues become resistant to insulin's effects, the pancreas compensates by producing more insulin, leading to hyperinsulinemia. High insulin levels are directly toxic to the lamellar tissues of the hooves, triggering the vascular and cellular dysfunction that leads to laminitis. This creates a vicious cycle where metabolic dysfunction promotes fat accumulation, which worsens insulin resistance, which increases laminitis risk.

Early warning signs of Equine Metabolic Syndrome often develop gradually and may be normalized by owners who attribute them to the horse's breed characteristics or individual variation. Regional fat deposits are often the first visible sign, with fat accumulating in the crest of the neck, over the shoulders, in the loin area, and around the tailhead. The crest may become firm or hard rather than soft and pliable, indicating the metabolic activity of this fat depot. General obesity may be present but is not universal, as some EMS horses maintain relatively normal body weight while having significant regional adiposity. The horse may be an easy keeper that gains weight readily on amounts of feed that would be insufficient for other horses.

The most significant clinical symptoms of EMS relate to laminitis, which may range from subtle footsoreness to acute, severe lameness. Horses may show mild gait stiffness or shortened stride that is dismissed as routine soreness. Increased digital pulses in the feet and warmth over the hoof walls indicate inflammation in the lamellar tissues. The horse may adopt a characteristic laminitic stance, shifting weight backward onto the heels to relieve pressure on the painful toe regions. In acute laminitis episodes, the horse may be severely lame, reluctant or unable to walk, and may lie down frequently to relieve pain. Recurring episodes of mild footsoreness, particularly in spring and fall when pasture sugar content fluctuates, strongly suggest underlying EMS.

Behavioral changes in horses with EMS may be subtle but observable with careful attention. Lethargy and reduced willingness to exercise may reflect the systemic effects of metabolic dysfunction or early foot discomfort. Horses may seek soft footing preferentially and be reluctant to walk on hard or rocky surfaces. Appetite typically remains excellent or may be increased, as the insulin dysfunction impairs satiety signaling. Some owners report their horses seeming stiff or sore after turnout or exercise that previously caused no problems. Changes in grazing patterns, with horses seeking out particular areas of pasture or appearing to target certain plants, may indicate metabolic instability.

Physical signs of EMS extend beyond the characteristic regional fat deposits and laminitis. The neck crest in severely affected horses may become so enlarged and firm that it falls to one side, a finding that indicates advanced metabolic dysfunction. Abnormal fat pads may be visible or palpable over the tailhead, giving a shelf-like appearance when viewed from behind. Divergent growth rings on the hooves, with rings closer together at the toe than at the heel, indicate past episodes of laminitis and lamellar damage. White line widening and stretched laminae visible on the solar surface of the hoof reflect chronic structural changes from recurrent or chronic laminitis. Dished hoof walls and dropped soles may be present in severe cases.

Symptom progression in EMS typically follows a pattern of worsening metabolic dysfunction and increasing laminitis risk if the condition is not managed. Horses that initially showed only regional adiposity may develop progressively more severe obesity and more pronounced fat deposits. Insulin dysregulation often worsens over time without intervention, with baseline insulin levels rising and responses to oral carbohydrates becoming increasingly exaggerated. Laminitis episodes may become more frequent and more severe, with each episode potentially causing additional permanent damage to the hooves. Eventually, horses may develop chronic laminitis with permanent structural changes that limit their soundness even between acute episodes.

Emergency symptoms requiring immediate veterinary care include any signs of acute laminitis such as severe reluctance to walk, bounding digital pulses, heat in the hooves, and the classic laminitic stance with weight shifted backward. Horses that cannot or will not stand require emergency intervention to prevent permanent hoof damage. Lying down for extended periods due to foot pain is a critical finding. Recumbent horses that cannot rise need immediate veterinary attention. Even less severe signs such as mild footsoreness following dietary changes, pasture access during high-risk periods, or other metabolic challenges warrant prompt veterinary evaluation to prevent progression to more severe laminitis.

Physical examination of a horse suspected of having EMS includes systematic evaluation of body condition and fat distribution. Body condition scoring using standardized systems helps quantify the degree of obesity and identify regional fat accumulation. The cresty neck score specifically grades the size and firmness of the neck crest on a scale from zero to five, with higher scores indicating more severe metabolic fat deposition. Fat deposits in other characteristic locations should be palpated and graded. The hooves should be carefully examined for evidence of current or past laminitis, including digital pulses, hoof wall warmth, hoof wall rings, and structural changes. A thorough lameness evaluation determines whether active laminitis is present. Weight estimation using a weight tape provides baseline measurement for monitoring.

Diagnostic testing for EMS centers on documenting insulin dysregulation, the defining metabolic abnormality of the condition. Resting or basal insulin measurement provides initial screening information, with elevated fasting insulin levels supporting the diagnosis. However, normal resting insulin does not rule out EMS, as some affected horses maintain normal baseline levels while having exaggerated responses to carbohydrate challenge. Oral sugar test or oral glucose tolerance testing assesses the dynamic insulin response to oral carbohydrate, revealing the characteristic hyperinsulinemic response that indicates EMS. Glucose levels are measured alongside insulin to assess glucose tolerance. The combined glucose-insulin ratio and other calculated indices help characterize the severity of insulin dysregulation.

Advanced diagnostics may be indicated to fully characterize metabolic dysfunction and rule out concurrent conditions. Testing for Pituitary Pars Intermedia Dysfunction using ACTH measurement is important because PPID commonly occurs alongside EMS, particularly in older horses, and the conditions require different treatment approaches. The TRH stimulation test may be used for more sensitive PPID detection. Thyroid hormone levels may be measured, though true hypothyroidism is rare in horses and low thyroid levels often reflect sick euthyroid syndrome rather than primary thyroid disease. Leptin levels, if available, correlate with adiposity and metabolic dysfunction. Radiographs of the feet should be obtained if laminitis is suspected or confirmed to document the position of the coffin bone and guide treatment and prognosis.

Differential diagnosis for horses presenting with obesity, regional fat deposits, or laminitis includes several conditions that may resemble or coexist with EMS. Pituitary Pars Intermedia Dysfunction can cause similar metabolic dysfunction and must be specifically tested for, particularly in horses over fifteen years of age. Simple obesity from overfeeding without underlying metabolic disease may be distinguished by normal insulin testing. Laminitis from causes other than insulin dysregulation, including supporting limb laminitis, septic laminitis, and laminitis from other endocrine disorders, requires consideration based on history and clinical presentation. Hypothyroidism has been historically overdiagnosed in obese horses but is rarely a primary cause of the phenotype seen in EMS.

Emergency treatment for horses with EMS presenting with acute laminitis focuses on immediate pain control, stabilization, and prevention of further lamellar damage. Pain management using appropriate analgesics, typically nonsteroidal anti-inflammatory drugs, is essential for horse welfare and to encourage the horse to remain standing. Cryotherapy through continuous ice water immersion of the affected feet has been shown to reduce lamellar damage during the acute phase and should be implemented as soon as possible after laminitis onset. Foot support using properly fitted frog supports or therapeutic shoeing helps redistribute weight away from damaged laminae. The horse should be confined to a deeply bedded stall with minimal forced movement. The precipitating dietary cause, if identifiable, should be immediately removed.

Medical management of ongoing EMS involves addressing the underlying insulin dysregulation through multiple approaches. Dietary management is the foundation of treatment, with severe restriction of nonstructural carbohydrates from all sources. Levothyroxine sodium has been used to increase metabolic rate and promote weight loss, though its effects on insulin sensitivity are debated and it should not be used as a substitute for proper dietary management. Metformin, an insulin-sensitizing drug used in human type 2 diabetes, has been investigated for equine use with variable results and is sometimes prescribed as adjunctive therapy. SGLT2 inhibitors, a newer class of medications that reduce blood glucose by promoting renal glucose excretion, are being researched for equine metabolic disease.

Dietary management is the cornerstone of EMS treatment and must be implemented rigorously and consistently. All grain-based feeds, sweet feeds, and high-carbohydrate supplements should be eliminated entirely. The diet should be based on grass hay with documented low nonstructural carbohydrate content, ideally less than ten percent NSC on dry matter basis. Hay should be soaked in water for thirty to sixty minutes before feeding to leach out soluble sugars if low-NSC hay is not available. Total daily hay intake should be limited to approximately one and a half to two percent of body weight to promote gradual weight loss in obese horses. A ration balancer or vitamin and mineral supplement ensures nutritional adequacy without adding significant calories.

Supportive care for EMS horses includes exercise programming, hoof care, and ongoing monitoring. Regular exercise is essential for improving insulin sensitivity and promoting weight loss, with programs designed according to the horse's current fitness and soundness. Horses recovering from laminitis may begin with hand walking and progress gradually as lameness resolves. Hoof care should address any laminitic changes and may include therapeutic trimming and shoeing to optimize comfort and biomechanics. Body weight should be monitored regularly using weight tapes or scales to track progress. Body condition scoring at regular intervals documents changes in regional fat deposits.

Rehabilitation and return to work for EMS horses depends on the severity of any laminitic damage and the success of metabolic management. Horses that have not experienced laminitis or have fully recovered can typically return to full work with appropriate management. Those with residual lameness or permanent hoof damage may require modified work expectations or may be limited to light exercise. The return to work process should be gradual, allowing conditioning to build without overwhelming metabolic or structural capacity. Exercise actually benefits EMS management through improved insulin sensitivity, so maintaining horses in work is encouraged when soundness permits.

Treatment decisions for EMS must account for the chronic nature of the condition and the commitment required for successful management. Owners must understand that EMS management is lifelong and requires permanent dietary and lifestyle modifications. The costs of management include not only veterinary care and specialized feeds but also the time and effort required for exercise programs, hay soaking, and restricted turnout. Horses with severe, recurrent laminitis that does not respond to management may have limited quality of life, and honest discussions about prognosis and long-term expectations are important. For most horses with EMS, however, proper management allows comfortable, useful lives.

The recovery timeline for EMS depends on what aspect of the condition is being addressed. Metabolic improvement, as measured by insulin levels and dynamic testing, may begin within weeks of implementing dietary changes and exercise, though significant improvement typically takes two to four months or longer. Weight loss, if the horse is obese, should proceed gradually at a rate of approximately one to two percent of body weight per week to avoid triggering hyperlipemia, a dangerous condition of fat mobilization. Regional fat deposits, particularly the hardened neck crest, may be the slowest to resolve and may never fully normalize in some horses. Recovery from laminitis episodes depends on the severity of lamellar damage and may range from days for mild episodes to months for severe cases with structural damage.

Post-treatment care and monitoring require ongoing vigilance and regular reassessment. Body weight should be monitored weekly during active weight loss programs and monthly once target weight is achieved. Body condition scoring every two to four weeks helps track changes in regional fat deposition. Insulin testing should be repeated periodically, typically every three to six months initially and then annually once stable, to confirm that metabolic control is being maintained. Hoof health requires constant attention, with hoof growth patterns, digital pulses, and any subtle gait changes monitored regularly. Any signs of returning footsoreness or weight gain should prompt immediate review and intensification of management.

Prognostic factors for EMS management success include the severity of insulin dysregulation at diagnosis, the horse's response to dietary changes, the presence and severity of laminitis history, and the owner's ability to maintain appropriate management long-term. Horses with mild to moderate insulin dysregulation that is identified before significant laminitis has occurred have excellent prognoses with proper management. Those with severe, longstanding metabolic dysfunction or extensive laminitis history face more guarded prognoses. Owner compliance is critical, as lapses in dietary management can quickly undo months of progress. Horses whose environments can be controlled to prevent unauthorized feeding and managed pasture access tend to do better than those in situations where management consistency is difficult.

Long-term soundness outlook for EMS horses depends primarily on the laminitis history. Horses that have never had clinical laminitis or have had only mild, well-managed episodes can expect excellent long-term soundness with continued appropriate management. Those that have experienced severe or recurrent laminitis may have permanent structural changes in the hooves that affect soundness to varying degrees. Even with chronic changes, many horses can be maintained comfortably for their intended use through proper trimming, therapeutic shoeing, and continued metabolic control. The key is preventing further laminitic episodes through rigorous management, as each episode risks additional permanent damage.

Management practices to prevent Equine Metabolic Syndrome and its complications begin with recognizing at-risk horses before problems develop. Horses of predisposed breeds should be managed with the assumption that they may be metabolically sensitive, with careful attention to diet and body condition from an early age. Body condition should be monitored regularly, with action taken promptly if weight gain or regional fat accumulation is observed. Feeders should be cautious about the tendency to overfeed, recognizing that many horses need far less food than owners typically provide. Management systems should be designed to promote movement and exercise rather than allowing horses to stand idle in small areas.

Nutritional prevention centers on avoiding the dietary factors that drive obesity and insulin dysregulation. Diets should be based on appropriate amounts of quality forage rather than calorie-dense concentrate feeds. Grain-based feeds, sweet feeds, and high-sugar treats should be avoided entirely or used very sparingly for at-risk horses. Hay selection should consider sugar and starch content, with low-NSC hay preferred for metabolically sensitive horses. Pasture management requires attention to grass composition and timing of access, with restriction during high-risk periods when grass sugar content peaks. Feeding amounts should match actual caloric needs based on body condition and work level rather than following generic feeding guidelines.

Exercise and conditioning provide powerful protection against EMS through multiple mechanisms. Regular physical activity improves tissue sensitivity to insulin, allowing more efficient glucose handling with lower insulin levels. Exercise burns calories, helping to prevent the positive energy balance that leads to obesity. Cardiovascular fitness improves overall metabolic function. Horses in consistent work programs are less likely to develop EMS than sedentary horses, even when other factors are similar. For at-risk horses, exercise should be viewed as a management requirement rather than an optional enhancement, with programs designed to provide regular activity appropriate to the horse's fitness and soundness.

Environmental factors influence EMS risk through their effects on diet and exercise. Pasture composition and management significantly affect metabolic challenge, with lush, fertilized pastures posing greater risk than sparse native grazing. Turnout systems that encourage movement, such as track systems or large paddocks with distributed resources, provide exercise benefits compared to confinement in small areas. Barn design and daily routines affect how much horses move throughout the day. Social grouping can influence eating patterns and stress levels. Overall, management systems should be designed to approximate the conditions under which horses evolved, with regular movement and limited access to concentrated calories.

Regular veterinary monitoring allows early detection of developing metabolic problems. Baseline insulin testing for at-risk horses establishes normal values for the individual and allows early detection of changes. Annual or biannual insulin screening is reasonable for horses of predisposed breeds or with concerning body condition. Physical examination with attention to body condition and regional fat deposits should be part of routine veterinary visits. Early intervention when abnormalities are detected prevents progression to clinical disease and the development of laminitis.

Daily management adjustments for horses with EMS require consistent attention to diet, exercise, and monitoring. Feeding routines should be established and followed precisely, with measured amounts of appropriate feed provided at regular times. Hay should be soaked if necessary to reduce sugar content, with soaking and draining completed before feeding to avoid fermentation. Water intake should be monitored, with fresh water always available. Exercise should be provided daily or near-daily according to the horse's fitness level and soundness. Weight monitoring using a weight tape at consistent conditions provides ongoing feedback about management effectiveness. Any changes in digital pulses, gait quality, or foot comfort should be noted and addressed promptly.

Housing and turnout considerations for EMS horses center on controlling dietary intake while providing opportunities for movement. Traditional pasture turnout is often not appropriate for EMS horses due to the difficulty of controlling grass intake, which varies dramatically with growing conditions, time of day, and season. Dry lot turnout, where horses are kept on dirt or gravel surfaces and fed measured amounts of hay, provides the control needed for dietary management. If pasture access is provided, it should be strictly limited in duration and timing, with grazing muzzles used to reduce intake. Track systems that encourage movement while limiting grazing are an option for some properties. Turnout companions should be chosen carefully to avoid competition for food.

Exercise modifications for EMS horses depend on soundness and fitness. Horses that are sound should be exercised regularly, with the type and intensity appropriate to their conditioning and the owner's goals. Hand walking, lunging, round pen work, trail riding, and arena work all provide benefits. Exercise should be consistent rather than sporadic, as regular activity provides ongoing metabolic benefits. Horses recovering from laminitis may need restricted exercise until soundness returns, followed by gradual reintroduction of work. Swimming or underwater treadmill exercise may be options for horses that cannot tolerate ground exercise. The goal is to maintain the highest level of activity appropriate for the individual.

Monitoring and ongoing care establish the foundation for successful long-term EMS management. Regular weighing tracks body weight trends. Body condition scoring documents changes in regional fat deposition over time. Hoof examinations, performed by owners between farrier visits, detect early signs of laminitis before they become severe. Regular farrier care maintains hoof health and addresses any mechanical issues. Veterinary examinations at least annually, and more frequently for horses with active problems, allow professional assessment and adjustment of management plans. Blood testing for insulin and ACTH levels monitors metabolic control and screens for concurrent PPID. Records of feeding, exercise, body weight, and any problems observed help identify patterns and guide management decisions.

Quality of life and use considerations for EMS horses require honest assessment of what each individual can safely do. Many EMS horses can continue in full athletic careers with appropriate management, competing successfully while adhering to dietary restrictions. Others may be limited to light pleasure use or trail riding. Horses with severe, refractory laminitis may be best suited as companion animals if they can be kept comfortable. The quality of life depends not just on soundness but on the horse's ability to live a life that meets equine behavioral needs for movement, social interaction, and mental stimulation within the constraints necessary for metabolic control. Management should aim to optimize quality of life rather than simply preventing laminitis.

Breeds at particularly high risk for Equine Metabolic Syndrome include pony breeds from the British Isles and similar native ponies from other regions. Welsh ponies and cobs, Shetland ponies, Connemara ponies, Highland ponies, and Fell ponies all show elevated susceptibility, likely reflecting adaptation to the sparse grazing and harsh conditions of their native environments. These breeds evolved to thrive on limited resources, an advantage in their original habitats but a liability when managed with abundant feed. American Miniature Horses share this metabolic profile despite their more recent development. Rates of EMS in some pony populations may exceed fifty percent when managed in typical domestic conditions.

Other breeds with increased EMS risk include Morgan horses, which demonstrate the easy-keeper phenotype that indicates metabolic efficiency. Paso Fino and Peruvian Paso horses are recognized as at-risk breeds. Arabian horses and their crosses may be predisposed, though this is less consistently documented than pony breed risk. Quarter Horses, particularly those bred for halter or pleasure rather than racing, show concerning rates of insulin dysregulation. Spanish breeds including Andalusians and Lusitanos have been mentioned as potentially at risk. Warmblood breeds can develop EMS, particularly when overfed and underworked. Draft breeds, especially when maintained as pets or light use horses with generous feeding, may develop metabolic dysfunction.

Genetic testing specifically for EMS predisposition is not currently available, as the genetic variants responsible have not been fully identified despite research efforts. However, breed and family history provide useful information for risk assessment. Breeding decisions should consider metabolic health, with horses showing significant insulin dysregulation or recurrent laminitis generally not selected for breeding. Offspring of affected horses should be managed as high-risk from birth, with dietary restriction and regular exercise implemented before problems develop. Until genetic testing becomes available, phenotypic assessment of body condition, regional fat distribution, and insulin testing provide the best information for identifying at-risk individuals.

Several conditions commonly co-occur with Equine Metabolic Syndrome, complicating management and affecting prognosis. Pituitary Pars Intermedia Dysfunction and EMS frequently occur together, particularly in older horses, with one study finding concurrent PPID in over thirty percent of EMS horses. The combination of these conditions creates especially high laminitis risk and requires management of both conditions simultaneously. Laminitis is the most clinically significant consequence of EMS, representing the condition that causes lameness, necessitates treatment, and in severe cases leads to euthanasia. Obesity, while often considered part of the EMS phenotype itself, contributes to and exacerbates insulin dysregulation, creating a feed-forward cycle of metabolic dysfunction.

Conditions with symptoms similar to EMS require careful differentiation through appropriate diagnostic testing. PPID causes metabolic dysfunction that may initially appear similar to EMS but involves different underlying mechanisms and requires specific treatment with pergolide. Hypothyroidism has historically been incorrectly diagnosed in obese horses but is rarely the primary cause of the metabolic phenotype. Simple obesity from overfeeding without underlying metabolic disease may be distinguished by normal insulin testing results, though the distinction is not always clear-cut. Laminitis from causes other than insulin dysregulation, including supporting limb laminitis and septic laminitis, must be considered based on clinical context.

Potential complications of EMS extend beyond laminitis to affect multiple body systems. Chronic inflammation associated with metabolic dysfunction may contribute to various health problems. Hyperlipemia, a dangerous condition of fat mobilization into the bloodstream, can occur in ponies and other susceptible horses during periods of caloric restriction, requiring careful management of weight loss programs. Regional fat deposits, particularly severe cresty necks that fall to one side, can themselves cause mechanical problems and are associated with higher metabolic risk. Reproductive problems including irregular cycling and reduced fertility have been associated with metabolic dysfunction in mares. Progression to frank diabetes mellitus, while rare, can occur in horses with severe, prolonged insulin dysregulation.