New study sheds light on managing PPID horses and the risk of laminitis

Research reveals pergolide’s role in insulin regulation – but diet still matters

A new study by the University of Melbourne, in collaboration with Spillers has brought fresh insight into managing horses and ponies with pituitary pars intermedia dysfunction (PPID) – often referred to as Cushing’s syndrome. The findings could prove valuable in helping reduce the risk of laminitis, a painful and often debilitating condition.

The research, recently highlighted in the Equine Veterinary Journal’s early view section as one of the most clinically relevant studies, focuses on how the commonly used drug pergolide mesylate affects insulin levels. PPID frequently occurs in older horses and ponies and can be further complicated when insulin dysregulation (ID) is also present – a combination known to significantly raise the risk of laminitis.

Pergolide is already widely used to help manage PPID’s clinical signs, but this study set out to explore its impact on insulin response – a crucial factor in laminitis risk.

To investigate, researchers monitored 16 senior horses – eight with both PPID and ID, and eight with ID alone – using a standardised meal test. Each horse underwent the test twice – once after four weeks on pergolide and once without the medication. Blood insulin levels were measured before and after consumption of a high-starch meal.

Key findings included:

• Pergolide reduced post-meal insulin levels in horses with both PPID and ID, bringing them in line with those seen in horses with ID alone.
• Horses with ID only saw no change in insulin response when treated with pergolide.
• Even with pergolide, horses with PPID and ID still produced insulin levels higher than those of healthy horses when fed a starchy meal.

Spillers Product Manager Sarah Nelson said: “The results suggest that pergolide may reduce the amount of insulin produced in response to eating in horses and ponies that have PPID together with ID but not back to normal.

“However, it is also important to note that sugar and starch can still raise insulin to abnormally high levels even when the horses and ponies are on pergolide, meaning that a low-sugar and low-starch diet remains crucial for horses with PPID and/or ID.

“Finally, given that horses with ID only did not respond to pergolide we must ensure that PPID and ID are tested for separately – managing one will not necessarily manage the other.”

The research supports the growing understanding that hyperinsulinaemia – high blood insulin – is the most common form of laminitis in the UK. While pergolide plays a role in regulating insulin response in certain cases, it’s not a standalone solution. Feeding a diet low in sugar and starch continues to be essential, even when horses are receiving medical treatment.