Author C.S. Lewis once said, “A myth is a lie that conveys the truth.” That’s what makes it so important to communicate the facts about pituitary pars intermedia dysfunction (PPID), previously known as “equine Cushing’s disease, one of the most common diseases of the equine endocrine system. May is PPID Awareness Month, the perfect time to learn more about PPID, how to identify it, and when to call your veterinarian.
WHAT IS PPID?
With PPID, the pituitary gland works overtime in the horse, resulting in hormonal imbalances that can disrupt normal body functions and result in a variety of physical health issues.
More specifically, PPID occurs as follows: The hypothalamus and pituitary gland, which set at the base of the equine brain, serve as the command center for the production of hormones. These chemical messengers are distributed around the horse’s body via the bloodstream to other tissues.
In a normal horse, these exist in balance and play an important role in maintaining and controlling body functions. With PPID, nerves in the hypothalamus undergo progressive degeneration and produce insufficient quantities of dopamine, a neurotransmitter. Dopamine is important for controlling the secretions of a part of the pituitary gland called the pars intermedia, which is responsible for controlling the secretion of certain hormones.
When the pars intermedia is not exposed to enough dopamine from the hypothalamus, it results in the production of abnormally high levels of these hormones, which leads to the clinical signs associated with the disease.
HOW COMMON IS PPID?
Research suggests 21 percent of horses and ponies 15 years of age and older are affected by PPID. However, more recently, horses as young as 5 years of age (although young age is uncommon), have been diagnosed with PPID.
HOW DO YOU DIAGNOSE PPID?
Signs of PPID may be erroneously attributed to aging in the animal or may go unrecognized until the disease is in the advanced stages. The signs also can vary widely, ranging from early or minimal to advanced.
If a horse owner notices any of these signs, they should contact their veterinarian to determine if PPID testing is warranted.
Recommended tests, which are administered by the veterinarian via blood test, include the TRH stimulation test measuring ACTH in horses with early PPID or in horses with clinical signs and a normal resting ACTH. Resting ACTH is recommended in horses with moderate to advanced signs of PPID.
HOW DO YOU TREAT AND MANAGE PPID?
There is no cure for PPID, but there is available treatment for the clinical signs of the disease. And when it comes to treating PPID, the earlier the better. Although some early signs can be managed (eg, extra clipping and grooming to control hypertrichosis), it is recommended that horses start medical treatment when clinical signs are initially recognized.
By using Prascend® (pergolide tablets) as part of your PPID management protocol, you can help control the signs of PPID and improve horses’ quality of life. Horses Treated with PRASCEND:
- Showed improved clinical signs within 3 months and continued through 6 months
- 3 out of 4 horses evaluated were considered treatment successes
- Hypertrichosis (delayed shedding) improved in 89% of treated horses within 6 months
In addition, scheduling regular veterinary visits is an important part of managing PPID. The veterinarian can help ensure proper dosing is being administered and make sure clinical signs are not advancing.
HOW DO YOU MANAGE PPID?
Regular Care from Hoof to Teeth
- Maintain proper hoof care, and communicate any abnormal observations to your veterinarian and farrier. Contact your veterinarian if any abnormal hoof wall growth or lameness issues are observed.
- Regular dental exams (teeth floating as needed)
Body Clipping, If Needed
- Many horses with PPID fail to shed out completely in the spring or, at the very least, shed later than herd or stable mates. The winter coat that “fails to shed” may include the entire hair coat (all over the horse’s body), or may just be a specific area of the horse’s body; for example, the side of the neck.
Deworm Regularly (Following recommendations from your veterinarian)
- Horses with PPID also have been shown to have higher fecal egg counts, suggesting that they are more susceptible to harboring internal parasites.
Properly Vaccinate Your Horse (According to recommendations from your veterinarian)
- Horses with advanced PPID have been shown to have an insufficient immune response following vaccination for West Nile virus. Based on this information, it was recommended that horses with advanced PPID should be considered for twice yearly vaccination for WNV.
Diet and Exercise
- Your veterinarian can advise you on a customized diet and exercise plan that will help your horse maintain the correct body weight. Your horse’s overall body condition (lean or overweight) may determine the type of nutrition plan recommended by your veterinarian. Horses with PPID often do well on low-sugar, low-starch diets, if considered prone to laminitis.
IMPORTANT SAFETY INFORMATION: PRASCEND is for use in horses only. Treatment with PRASCEND may cause loss of appetite. Most cases are mild. Weight loss, lack of energy, and behavioral changes also may be observed. If severe, a temporary dose reduction may be necessary. PRASCEND has not been evaluated in breeding, pregnant or lactating horses, and may interfere with reproductive hormones in these horses. PRASCEND tablets should not be crushed due to the potential for increased human exposure. Refer to the package insert for complete product information.
1 Ireland JL, McGowan CM. Epidemiology of pituitary pars intermedia dysfunction: A systematic literature review of clinical presentation, disease prevalence and risk factors. Vet J. 2018 May;235:22-33.
2 Grubbs ST, Neal DL and TJ Keefe. Clinical signs associated with PPID status in a large population of horses. J Vet Intern Med. 2015;29:1242.
3 Schott H, Andrews F, Durham A, et al. 2019 Equine Endocrinology Group, Pituitary Pars Intermedia Dysfunction Recommendations. Available at: https://sites.tufts.edu/ equineendogroup/files/2019/12/2019-PPID_EEGbooklet.pdf. Accessed April 2, 2020.
4 Schott HC. Pituitary pars intermedia dysfunction: challenges of diagnosis and treatment. In: Proceedings from the 52nd American Association of Equine Practitioners Annual Convention; December 2-6, 2006; San Antonio, TX.
5 PRASCEND® (pergolide tablets) [Freedom of Information Summary]. St. Joseph, MO: Boehringer Ingelheim Vetmedica, Inc.; 2011.
6 Frank N, Andrews F, Durham A, et al. 2015 Equine Endocrinology Group, Pituitary Pars Intermedia Dysfunction Recommendations. Available at sites.tufts.edu/ equineendogroup/files/2015/12/2015-10-16_EEG-2015-recommendations.pdf
7 McFarlane D, Hale GM, Johnson EM, Maxwell LK . Fecal egg counts after anthelmintic administration to aged horses and horses with pituitary pars intermedia dysfunction. J Am Vet Med Assoc. 2010;236(3):330–334.
8 Adams A, Siard M, Reedy S, et al. Does equine pituitary pars intermedia dysfunction affect immune responses to vaccination? AAEP Proceedings, Salt Lake City, Utah. 2014; 330 – 331.
9 McFarlane D. Equine pituitary pars intermedia dysfunction. Vet Clin North Am Equine Pract. 2011;27(1):93–113