Endocrine and Metabolic Disorders in our Horses
By Kelly Stalpes, DVM

As our horses age, they become more likely to develop endocrine and metabolic disorders. One of the most common diseases of horses and ponies 15 and older is a condition called Equine Pituitary Pars Intermedia Dysfunction (PPID), also known as Equine Cushing’s Disease.

PPID is a progressive neurodegenerative disorder of teenaged and older horses caused by abnormalities in the hypothalamus and pituitary gland, which are situated in the brain and help control hormone production. The result is over secretion of several hormones, including Adrenocorticotropin Hormone (ACTH) from the pituitary, and increased cortisol release from the adrenals. When diagnosing this disorder, ACTH is one of the hormones we can measure.

Classical signs of PPID include the long hair coat (hirsutism), laminitis, sweating, fat accumulation (ie: cresty neck), or increased urination and defecation. However, some of these signs, such as the long and curly coat, don’t typically occur until years after the start of pituitary dysfunction. PPID can also make horses prone to secondary infections. Once diagnosed, treatment with a medication called pergolide (Prascend) is indicated because this is a progressive disease and controlling the excess hormone secretion can help prevent the classical signs, laminitis being the most concerning. Regular trimming and shoeing are important to keep your horse’s feet healthy. PPID horses are also more prone to infections, so regular dental care is important to prevent gum disease.

Another common endocrine and metabolic disease in horses is Equine Metabolic Syndrome (EMS). EMS can have some shared clinical signs with PPID, such as regional fat deposition (ie: cresty neck) and laminitis, and it can also occur concurrently with PPID. This disease results from a disorder of insulin regulation, where the tissues become less responsive to insulin, so more insulin is secreted. Leptin is also produced by fat cells in increased quantities with this disorder. For this reason, insulin and leptin are evaluated to determine if a horse has EMS. EMS does not have a medication that fixes the insulin resistance. Instead, treatment relies on exercise and a diet low in sugars and starches because sugars induce further insulin release, and high insulin levels have been found to have a high association with laminitis.

If you any questions or concerns about endocrine and metabolic disorders and your horse, please contact your veterinarian. These disorders result in more than just cosmetic changes, and may cause more serious conditions that require additional treatment. Please call the clinic at 963-2371 if you have any questions or concerns about PPID or EMS and your horse.