Metabolic and endocrine disorders in horses encompass conditions like equine metabolic syndrome (EMS), insulin dysregulation (ID), pituitary pars intermedia dysfunction (PPID or Cushing’s), and thyroid or electrolyte imbalances that affect health and performance. These disorders can cause a variety of clinical signs such as: weight changes, abnormal fat distribution (i.e. cresty neck, fat pockets), recurrent laminitis, poor haircoat or shedding, lethargy, and altered exercise tolerance. Diagnosis relies on a combination of history, physical exam, bloodwork (insulin, ACTH, glucose, dynamic testing when indicated), and monitoring. Management focuses on diet and weight control, tailored exercise programs, medical therapies when needed (e.g., pergolide for PPID), hoof care to prevent laminitis, and ongoing monitoring to reduce complications and preserve function. Early recognition and a coordinated, long‑term plan improve comfort, reduce laminitis risk, and support longevity for all types of equids.
What is PPID?
PPID is short for pituitary pars intermedia dysfunction and is also referred to as Cushing’s disease. PPID is caused by a tumor of the pituitary gland in the brain that secretes an overabundance of ACTH (a hormone) among other things. The increased ACTH signals the adrenal glands to release more cortisol, and in a normal horse, the resulting increased cortisol causes the release of ACTH to stop. In a horse with PPID, the pituitary tumor will continue to signal for more and more cortisol and over time, we start to see clinical signs (symptoms). Some of the most classic signs of PPID include a long, thick haircoat, loss of topline, lethargy, fat deposition, laminitis, and increased drinking and urination. These signs are often found in horses with more advanced cases. More subtle signs include delayed shedding, exercise intolerance, a “potbelly” appearance, abnormal sweating, and increased susceptibility to illness or infection. PPID is diagnosed via blood test, which varies depending on the time of year. PPID is manageable with medication and diet changes. Give the clinic a call if you have questions about your horse!
What is Insulin Dysregulation?
Insulin Dysregulation (ID) is when insulin levels are not controlled normally in a horse’s body, resulting in sustained elevations over time. Insulin is a hormone that is secreted when food is eaten and the energy from it (glucose) needs to be stored. In a normal horse, insulin levels follow a similar curve to glucose. In a horse with ID, insulin can be high in the presence or absence of glucose elevations. High levels of insulin can be caused by excessive production or inadequate removal from the bloodstream. Insulin dysregulation is not the same as insulin resistance. Insulin resistance describes when insulin-responding tissues no longer respond to it, while insulin dysregulation simply describes abnormal levels or patterns. This is to say, all horses with insulin resistance have insulin dysregulation, but not all horses with insulin dysregulation have insulin resistance. Horses with ID are at an increased risk of laminitis and obesity, so testing is important to identify at-risk horses so we can treat accordingly. Horses with ID can be managed medically and most importantly, with diet and exercise.
What is Equine Metabolic Syndrome?
Equine Metabolic Syndrome (EMS) is used to describe a blend of clinical signs that coincide with insulin dysregulation. To have EMS, horses will have insulin dysregulation and additional clinical signs such as obesity, high triglycerides in their bloodstream, and hypertension. EMS overlaps with both PPID and insulin dysregulation. Bloodwork is essential to rule in/out PPID and to guide treatment. EMS can be managed medically, with diet, and exercise.
