Pituitary pars intermedia dysfunction (PPID) is a disease that affects the hormone levels in a horse’s blood. This disease is similar to the human version of Cushing’s disease; however, PPID does not affect the same area of the pituitary gland in horses that Cushing’s affects in humans. This disease is common in older horses. It can cause the horse to lose muscle and energy.
Recently, researchers devised a new plan that can enable veterinarians to detect the disease much earlier in its onset than before. Developed by the Equine Endocrinology Group (EEG), these new guidelines have better diagnostic tests for the purpose of identifying and treating PPID in its earliest stages.
Some horses have the disease but show no symptoms. Diagnostic tests include measurement of adrenocorticotropin hormone (ACTH) – a hormone secreted by the pituitary gland and a dexamethasone suppression test. Dexamethasone is a hormone that normally decreases cortisol levels. Additionally, the EEG guidelines require the veterinarian to order a thyrotropin-releasing hormone (TRH) stimulation test. If the horse has PPID, the TRH test will cause a horse with PPID to release hormones from the pituitary gland at a higher-than-average level. The TRH stimulation test is only effective in the months between December and June.