The most common endocrine disorders encountered by equine practitioners and owners are pituitary pars intermedia dysfunction (PPID or Cushing’s Syndrome) and equine metabolic syndrome (EMS).

The acronym PPID is more widely used for this disease, as it provides a more accurate name. Another acronym, pars intermedia pituitary adenoma (PIPA), is also occasionally used. Cushing’s disease in people and other mammals differs in some important aspects; the affected portion of the pituitary gland is different, thus the use of the human medical term “Cushing’s” can be misleading.² Pituitary pars intermedia dysfunction and equine metabolic syndrome are often encountered in aging horses and may present with several recognizable signs, including laminitis.³

In the normal equine pituitary gland, specific cells called melanotropes receive neural input from the hypothalamus, causing neurons to release dopamine. The dopamine then inhibits the intermediate lobe of the pituitary gland from producing several different hormones. In the diseased pituitary gland, the hypothalamic neurons degenerate, resulting in dramatically lower dopamine levels.²

Common signs of PPID in horses include:

• Failure to fully shed
• Long, curly coat (often along the jaw line with feathering near the fetlocks)
• Chronic infections
• Repeated occurrences of laminitis with hoof abscesses
• Excess sweating
• Polyuria/polydipsia (PU/PD)
• Lethargy
• Loss of muscle mass (in untreated horses)
• Pot-bellied appearance
• Infertility, or lack of estrus cycles
• Abnormal development of mammary glands

Equine Metabolic Syndrome (EMS) is a more recently described syndrome that shares some characteristics with PPID. Both of these disorders alter cortisol metabolism, though EMS appears to have no underlying connection to thyroid dysfunction. The pituitary gland functions normally in horses with this EMS. 

Common signs of EMS in horses include:

• Hyperglycemia
• Altered tissue-level cortisol activity
• Increased leptin concentrations
• Altered lipid metabolism with hypertriglyceridemia
• Increased expression of inflammatory cytokines
• Hypertension³

EMS is typically seen in middle-aged horses, and is more common in pony breeds, domesticated Spanish mustangs, Peruvian Pasos, Paso Finos, Andalusians, European Warmbloods, American Saddlebreds, and Morgan horses, which suggests a genetic predisposition to EMS.⁴

Diagnoses and treatments for PPID and EMS will differ, so it is important to have an experienced equine veterinarian diagnose horses suffering from the described symptoms.

Where to buy Pergolide

Pergolide is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. 

This product carries minimal potential drug interactions, however it is advisable to consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

²Durham, A. Endocrine Disease in Aged Horses. Vet Clin North Am Equine Pract. 2016 Aug; 32(2):301-15. 

³McFarlane, D. Equine pituitary pars intermedia dysfunction. Vet Clin North Am Equine Pract. 2011 Apr; 27(1):93-113.

⁴aaep.org.