Pituitary Pars Intermedia Dysfunction (PPID) in Horses

SIMPLE SUMMARY: Pituitary pars intermedia dysfunction is the most common endocrine disease of geriatric horses and affects quality of life, immunocompetence and athletic performance. Clinical signs of pituitary pars intermedia dysfunction can include hypertrichosis (a long hair coat), muscle atrophy, a pendulous abdomen, recurrent infections, lethargy, lameness, polydipsia, and polyuria (drinking and urinating more than normal). Awareness of endocrine diseases such as pituitary pars intermedia dysfunction in the equine community has increased in the recent years, and new research is becoming available providing insight into prevalence of clinical signs, difficulties with current diagnostic techniques, and treatment of the condition. The purpose of this article is to review the current literature, to provide veterinarians access to current perspectives for pathophysiology, clinical signs, diagnosis, and treatment of pituitary pars intermedia dysfunction. ABSTRACT: Substantial morbidity results from pituitary pars intermedia dysfunction (PPID) which is often underestimated by owners and veterinarians. Clinical signs, pathophysiology, diagnostic tests, and treatment protocols of this condition are reviewed. The importance of improved recognition of early clinical signs and diagnosis are highlighted, as initiation of treatment will result in improved quality of life. Future research should be targeted at improving the accuracy of the diagnosis of PPID, as basal adrenocorticotropic hormone (ACTH) concentration can lack sensitivity and thyrotropin releasing hormone (TRH) used to assess ACTH response to TRH stimulation is not commercially available as a sterile registered product in many countries. The relationship between PPID and insulin dysregulation and its association with laminitis, as well as additional management practices and long-term responses to treatment with pergolide also require further investigation.