Summary

Equine Cushing’s disease, also called Pituitary Pars Intermedia Dysfunction (PPID), is an age‑related endocrine disorder in horses caused by degeneration of dopamine‑producing nerve cells in the brain. Reduced dopamine leads to excessive ACTH release, stimulating the adrenal glands to produce high cortisol levels. This hormonal imbalance results in characteristic clinical signs. Diagnosis is made through blood testing, most commonly baseline ACTH levels or dexamethasone suppression testing, with additional tests such as TRH stimulation used in select cases. Because no test is perfect, ongoing monitoring of blood values and clinical signs is important. Treatment involves lifelong daily pergolide, a medication that increases dopamine levels and helps control symptoms. Common signs include abnormal hair growth and shedding, increased drinking and urination, weight and muscle loss, abnormal fat deposits, increased infection risk, and a significantly elevated risk of laminitis.