(Pars Pituitary Intermedia Dysfunction or PPID)

Pars Pituitary Intermedia Dysfunction, or PPID, is a condition in which the pars intermedia of the pituitary gland starts overproducing a hormone called ACTH.


The Pituitary Gland:

The pituitary gland is found on the underside of the brain, and is stimulated by another gland, the hypothalamus, to produce a number of hormones responsible for regulating many different body functions. Among these hormones is adrenocorticotrophic hormone, or ACTH.

ACTH stimulates the adrenal glands to produce corticosteroids, which play multiple roles in inflammation and metabolism. Usually, when too many steroids are being produced, the pituitary gland is able to downregulate the production of ACTH to counter this. ACTH levels vary naturally throughout the year, with a normal increase occurring in autumn when horses grow their winter coats.



In PPID, there is a benign enlargement of the pars intermedia and an increase in production of ACTH that the body cannot compensate for. It results in excessive steroids being produced, which have the following effects on the body:

  • Lethargy

  • Muscle wastage

  • Fat around the eyes

  • Drinking and urinating excessively

  • Abnormal hair retention

  • Recurrent infections

  • Laminitis


It’s estimated that 50% of horses over the age of 15 have PPID, and 75% of those over the age of 20.


PPID can be diagnosed by a simple blood test which quantitively measures the level of ACTH being produced by the pituitary.










PPID is easily treatable with a product called Prascend, which prevents the pituitary gland from overproducing ACTH. It is given in tablet form once a day. Levels of ACTH vary throughout the day, with a peak occurring in the morning, so Prascend is best given in the morning to counteract excessive ACTH when it is at its highest. PPID is a lifelong condition and so treatment with Prascend must also be lifelong. Side effects associated with Prascend are extremely rare, the most common of which is the horse going off its food when starting the tablets. In these circumstances we usually advise halving the dose for a week or so until the appetite is back to normal before resuming the full dose.




PPID is a slowly progressive condition, so it is important to ensure that your horse has regular check-ups and ACTH measurements to ensure he remains on the correct dose. We usually recommend retesting ACTH 4-6 weeks after starting Prascend to ensure the initial dose is having the desired effect, and then every 6 months after this.


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