New PPID Research Receives Special Recognition

New PPID research was published by The University of Melbourne in partnership with The WALTHAM Equine Studies Group.¹ It was selected as one of the most clinically relevant pieces of research published in the Equine Veterinary Journal’s early view section for the month.

The study evaluated the effect of pergolide mesylate on insulin dysregulation. This is helping to improve our knowledge of how best to treat and monitor pituitary pars intermedia dysfunction (PPID, also known as Cushing’s syndrome).

More than 20% of horses over the age of 15 and more than 25% of horses over the age of 20 might have pituitary pars intermedia dysfunction. Therefore, studies such as this play an important role in helping to ensure senior horses and ponies around the world are able to live happier, healthier lives for longer.

PPID, ID, Laminitis, and Pergolide

Many horses and ponies with PPID are insulin dysregulated. This puts them at increased risk of laminitis. In fact, laminitis associated with a high concentration of insulin the blood (hyperinsulinemia) is now thought to be the most common form of laminitis in many countries.

The exact link between PPID and insulin dysregulation (ID) is unclear. Not all horses with PPID have ID and not all horses with ID have PPID! PPID might exacerbate ID when the two conditions exist together.

The most common drug used to treat PPID is Pergolide mesylate. It has been shown to be effective in managing some of the main associated clinical signs. As laminitis is such a painful and potentially devastating condition, the researchers in this study were keen to find out whether pergolide might help to reduce ID.

PPID Research

As part of this study, 16 senior horses—eight with PPID and ID and eight with ID only—took part in a standard meal test. This involved measuring the concentration of insulin in their blood before and after eating a high starch meal.

By the end of the study, all horses had completed the standard meal test twice, once after 4-weeks of pergolide treatment and once without pergolide treatment.

Pergolide treatment reduced blood insulin levels after eating in horses with PPID and ID.
Pergolide treatment had no effect on blood insulin levels in horses with ID only.

What Does This Mean?

The results of this study are encouraging. They suggest that pergolide might limit the amount of insulin produced in response to eating in horses and ponies that have pituitary pars intermedia dysfunction in addition to ID. That, in turn, might help to reduce their risk of laminitis.

However, feeding a diet low in starch and sugar is still very important for horses with PPID and/ or ID because:

Even when treated with pergolide, the horses in this study produced higher levels of insulin in response to eating a starch and sugar rich meal than we see in healthy horses;
Pergolide had no effect on blood insulin levels in horses with ID only.

You must test for PPID and ID separately. If necessary, they should also be treated separately. The fact that horses with ID only did not respond to pergolide shows that managing one condition will not necessarily manage the other.

If you’re concerned about the possibility of PPID and/ or ID, speak to your vet and a nutritionist. Then, suitable management and/or treatment can be started as soon as possible.