In brief: Pituitary Pars Intermedia Dysfunction (PPID)

Definition: Also known as Cushing’s disease, PPID occurs when the pituitary gland produces excess amounts of adrenocorticotrophic hormone (ACTH). Elevated ACTH levels, in turn, lead to overproduction of cortisol, a hormone that regulates metabolism, the immune response and other body processes. The causes of PPID are unclear, but it’s common in older horses: Researchers estimate that more than 20 percent of horses older than 15 have PPID.

Signs: PPID causes a slew of systemic problems, including a long coat that is slow to shed, muscle weakness, compromised immune function and susceptibility to infection. Horses with PPID are also prone to chronic laminitis.

Treatment: PPID can be controlled with the medication pergolide, sold under the brand name Prascend. Pergolide works by binding with receptors in the brain that control the production of dopamine, decreasing the blood levels of ACTH. The medication is given daily and is very effective in reducing the signs of PPID.