If you’ve been involved with horses for even just a few years, chances are you’ve encountered at least one with pituitary pars intermedia dysfunction (PPID). Also known as Cushing’s disease, this endocrine disorder is common in older horses. In fact, studies estimate that 20 percent of horses over the age of 15 will develop PPID. Add in the fact that horses are living longer than ever before and it’s not surprising that most of us have some familiarity with the disorder.