Pituitary pars intermedia dysfunction (PPID), formerly known as equine Cushing's disease, and equine metabolic syndrome (EMS) are both serious diseases affecting a horse's endocrine system. At a glance, clinical signs for these two disorders may present similarly, though treatment and management for PPID and EMS differ. Being able to distinguish between the clinical signs of PPI D and EMS can result in an accurate diagnosis and proper management, resulting in a healthier horse.

PPID largely affects the hormone production pathways in the pituitary gland, resulting in increased levels of hormones produced by the pars intermedia of the pituitary gland. Early signs of PPID can be subtle and difficult to recognize, and may gradually worsen as the disease progresses. Early clinical signs of PPID can include delayed hair coat shedding, change in attitude, decreased performance, regional adiposity (fat deposits), abnormal sweating and laminitis.

Because early signs of PPID can be so subtle, Steve Grubbs DVM, Ph.D., DACVIM, Technical Services Veterinarian at Boehringer lngelheim, recommends monitoring your horse throughout the year to recognize potential clinical signs early on. "Things like loss of topIine muscle or regionaI areas that do not shed out may occur so gradually that you may not notice it day to day," he said. "At least twice a year, take a photo of your horse in the same place on the farm from the same angle that can be reviewed retrospectively, to identify subtle changes that have occurred over time."

In advanced PPID, delayed shedding may become more generalized, and progress to a complete loss of seasonal hair coat shedding. Other associated clinical signs, such as increased thirst and urination, and certain tendon/ligament injuries may develop. A horse with advanced clinical signs of PPID may also have immunosuppression, or a depressed immune system. This often results in recurrent infections, such as hoof abscesses, secondary skin infections and sinusitis.

Typically, clinical signs of EMS may present differently than clinical signs of PPID, although some overlap of signs may occur in certain horses. Diagnostics are often needed to differentiate between the two or identify if your horse has both PPID and EMS. "With EMS, phenotypically, we are usually looking at a horse that's overweight, obese or exhibiting regional adiposity or excess fat deposits," explained Dr. Grubbs. For these reasons, clinical signs may be masked in sport horses or horses that are in an active training program, only manifesting when the horse retires or is laid up due to injury.

Horses with EMS are also at a higher risk of laminitis, or founder. "With a horse that has EMS and is presenting as obese, one of the main goals is weight loss," stated Dr. Grubbs. "Small lifestyle changes, such as switching the horse's grain to a ration balancer; strictly limiting or managing time on pasture, no matter the time of year; and having hay analyzed to understand starch levels, can add up quickly and become crucial to management of a horse with EMS."

EMS can occur at any point in a horse's life, but may be first noticed around adulthood, after they've had time to put on noticeable weight. PPID typically occurs in horses over 70-75 years old, although in rare cases has occurred in horses as young as five. No matter their age, if you notice any clinical signs of either PPID or EMS it's important to contact your veterinarian right away. After collecting a medical history and examining your horse for clinical signs, your veterinarian will evaluate ACTH, insulin and glucose levels to determine the diagnosis.

Though neither EMS nor PPID can be cured, through proper management, lifestyle changes and medication, horses with both PPID and EMS can continue to live a long and healthy life.

©2024 Boehringer lngelheim Animal Health USA Inc., Duluth, GA. All Rights Reserved. US-EQU-0075-2024