How to Spot Metabolic Changes in Horses

Key Highlights

• Routine grooming and physical examination reveal subtle metabolic changes, regional adiposity, and abnormal fat deposits before an increased risk of laminitis becomes obvious.
• PPID (equine Cushing’s disease), EMS, and concurrent PPID cause insulin dysregulation; elevated baseline insulin and poor insulin regulation, shaped by environmental factors and dietary history, drive laminitis risk.
• Obesity, fat deposition (crest, tailhead, mammary glands), and exposure to soluble carbohydrates from grain and lush pasture amplify metabolic strain and hyperinsulinemia‑associated laminitis.
• Diagnostic testing (baseline insulin, ACTH, glucose, oral sugar test) plus imaging for conditions such as pedal osteitis helps assess risk and track movement toward or back toward the normal range.
• Management centers on low‑NSC forage, restricted soluble carbohydrates, slow feeding, and exercise to reduce regional adiposity, normalize amino acids/protein balance, and follow current consensus statement guidance for long‑term laminitis prevention.

Metabolic Conditions in Horses

• Metabolic issues, such as Cushing’s and Insulin Resistance, have major health implications for your horse in addition to increasing the chance of laminitis. These conditions slowly creep into your horse, making instant recognition difficult. It’s also critical to remember that your horse’s outward signs of health issues will come much later than what their bloodwork reveals.

Pituitary Pars Intermedia Dysfunction (PPID), formally known as Equine Cushing’s Disease

• The term pituitary pars intermedia dysfunction refers to the location of the problem. The middle lobe of the pituitary gland (pars intermedia) becomes overactive, enlarged, or develops a tumor. This area begins to secrete excessive hormones, especially adrenocorticotropic hormone (ACTH).

• This pituitary hormone signals the adrenal glands to produce cortisol and related steroids as part of the body’s stress and metabolic regulation system. With PPID, this action is overactive, which, in turn, leads to increased levels of other steroids and hormones, such as insulin, influencing the body.

• PPID and related hormone changes are the most common endocrine disease in older horses, ponies, and donkeys, affecting roughly 15–30% of horses aged 15 or older.

Equine metabolic syndrome (EMS) and insulin resistance (IR)

• Equine metabolic syndrome is a collection of conditions affecting metabolic health in horses. This endocrinopathy dictates that a horse can’t handle insulin properly and will lose insulin sensitivity. This process increases insulin levels despite normal blood glucose levels.

• Horses release insulin to help process blood sugars. Over time, the body becomes insulin-resistant, prompting the pancreas to produce more insulin to lower blood sugar levels. Insulin becomes a background noise to your horse’s body, increasing levels until they are “heard,” even if blood glucose levels are normal.

• EMS is especially common in “easy keeper” types such as ponies, donkeys, Morgans, Arabians, and mustangs, and is often compared to Type 2 diabetes in humans. While younger horses are less likely to develop PPID, they can still develop EMS, and these metabolic changes are especially likely with higher body weight.

• A diagnosis of EMS is not permanent, as smart dietary management and exercise to improve the body condition score can reduce the high risk of laminitis and push the condition away.

• Many horses with PPID also develop IR, but not all horses with IR have PPID.

This fuzzy coat (in August) is a sign of a metabolic issue. A fuzzy coat is not the only indicator – and just because your horse is NOT fuzzy doesn’t mean they don’t have a metabolic disorder.

The Risks of Laminitis with PPID and EMS

• PPID and EMS account for the majority of laminitis cases. In clinical studies, insulin is a trigger of laminitis in otherwise healthy horses and ponies. Horses with PPID are around 4 to 5 times more likely to have laminitis than their counterparts.

• PPID itself is a pituitary disease, but many PPID horses also develop insulin dysregulation; when PPID and hyperinsulinemia coexist, laminitis risk and lamellar lesions increase sharply.

• High insulin levels directly affect the laminae in the hoof. Hyperinsulinemia alters lamellar cell signaling and structure, eventually weakening the laminae and thereby affecting the attachments between the hoof wall and the coffin bone.

• This creates hyperinsulinemia-associated laminitis (HAL).

• Laminitis occurs in EMS and PPID horses even without other factors, like grain overload, road founder, fevers, supporting limb issues, or other causes of laminitis.

For deep dives into metabolic disorders in horses, read these works of art about Cushing’s and Insulin Resistance (IR).

How does EMS affect overall health and body condition?

• EMS horses often become overweight with cresty necks and fatty pads, develop poor fitness, and are highly prone to recurrent, sometimes severe laminitis. Chronic pain, reduced performance, and management challenges can significantly compromise welfare and long‑term usability.

Detecting Metabolic Disorders in Horses

• You have two primary ways to monitor your horse’s metabolic health. One is by daily handling and grooming, and the other is partnering with your veterinarian for bloodwork and health screenings. By the time you see the obvious red flags, which are often laminitis, these diseases have taken hold.

• Luckily, a blood test or two can be easily performed, and the management of such conditions is straightforward.

• Diet, diligence, and some medications can help your horse and lessen the risk of laminitis, which is clearly linked to metabolic issues.

• Some PPID horses with normal insulin levels may not have markedly increased laminitis risk, which is why guidelines emphasize always checking insulin, not just ACTH.

A simple blood draw and lab testing can give you loads of information. Not all horses with metabolic disorders look or act like they have a problem. Do the bloodwork!

Clinical Signs of Metabolic Changes in Horses

You may see clues to a changing metabolic status. It’s worth noting that these signs of metabolic changes are not set in stone, and the absence of them does not mean your horse is in the clear.

Changes in the hair coat

• Does your horse have longer or curlier hair than you remember from a few years ago? Is shedding difficult? Do you think your horse could benefit from clipping in the heat of summer? Not all hair horses have PPID, and not all with PPID have hair growing and shedding issues.

A cresty neck

• Thicker necks along the topline can indicate fat deposits or extra muscling.

Fat deposits in odd places

• Around the tail, the shoulder blades, and the flank, you may find squishy fat deposits. These don’t appear overnight, and are worth investigating. These fat pads are subcutaneous fat, meaning they are just under the skin and easy to feel.

A hay belly

• If your horse is looking like a puppy full of worms with a pendulous belly, it may be a metabolic disease.

Shrinking muscles

• Very often, horses will gain fat while losing muscle mass. A typical PPID horse loses topline and may show weight loss, while a typical EMS horse gains weight. These traits often overlap! It’s vital to track both muscle mass loss and fat gain.

Soreness after shoeing or grazing

• There is subclinical laminitis that presents as sore hooves, especially after a farrier visit or grazing. The sugars in grains and grasses can trigger a low-grade laminitis episode that may or may not fade away.

• You may also see growth rings on the hooves, indicating past trauma or episodes of laminitis.

An overall change of attitude and energy levels

• It’s so tricky to discern between aging, fitness, and overall energy levels. This vague sign could mean anything!

Becoming an air fern or easy keeper

• When your horse can glance sideways at food and gain weight, you know something isn’t right.

Laminitis

• Because laminitis is most closely associated with metabolic changes, an episode is likely directly linked to insulin levels. Ideally, this never happens, but it can.

The big picture

• Working with your veterinarian to assess your horse’s hidden health status is the most important thing you can do. Knowing their insulin concentration, ACTH, and glucose values long before you see signs of trouble will help your horse never experience devastating laminitis.

Testing for Metabolic Changes in Horses

• Spend a few dollars to have your horse tested for Insulin Resistance and Cushing’s Disease. By the time you see signs (like laminitis), the metabolic disorder is well underway.

• One method is the oral sugar test (OST). Your horse will fast for 12 hours, then receive a dose of corn syrup. About an hour later, blood is drawn to measure insulin responses. The sugar content in the corn syrup triggers insulin, and the fasted horse has the cleanest test, as they will react only to that corn syrup.

• Other blood tests measure insulin concentrations without the corn syrup and may involve diagnostic tests with dexamethasone, a steroid, instead.

• The time of year also plays a role in testing for elevated insulin and ACTH levels.

Monitor Your Horse’s Weight

• There is overwhelming research about the detrimental side effects of overweight horses. A recent study found that obese horses have DOUBLE the chance of developing laminitis. Use a weight tape regularly to monitor your horse’s status.

• Check their weight every few weeks. Take note of the season, too, as it’s natural in fall for ACTH levels to rise and for horses to gain weight ahead of winter.

• Have your vet perform a body composition analysis regularly to track changes in muscle and fat over time.

Slow feeders help all horses eat and digest better.

Lifestyle Changes Benefit Metabolic Changes in Horses

• Managing chronic diseases requires broad strokes and overall barn management changes. The goal is to reduce the overall risk of laminitis, maintain a healthy body size, and steady hormone levels to keep your horse comfortable. This isn’t done through severe calorie restriction, but rather through a healthy diet and regular exercise to support healthy aging.

• As PPID and EMS slow metabolism, the goal is to prevent muscle loss with appropriate exercise for cardiovascular health and to shrink fat tissue. You and your vet should create a fair and gradual fitness plan to build muscle tissue, reduce visceral fat, and support overall healthy weight management.

• Appropriate dietary ingredients play an important role in supporting healthy metabolic function and preventing muscle loss. Reduce dietary sugars and starches, adjust protein levels, and supplement with appropriate ingredients that help metabolic processes.

• Use slow-feeding methods like hay nets or bags and grazing muzzles to promote a healthier eating pattern. This can help prevent ulcers, prevent excessive weight gain, and reduce laminitis risk by reducing the amount of sugar entering the hindgut.

Remember, any change in your horse is a sign of something! Talk to your veterinarian to determine why, and find out how to help your horse thrive again. And keep being a diligent, observant horse owner as you take amazing care of your horses.