Pituitary Pars Intermedia Dysfunction and Metabolic Syndrome in Donkeys

Abstract

Appropriate medical care for donkeys is challenging despite being important working animals in non-industrialized countries and pets in first world countries. Although the same principles of diagnosis and therapy as in horses are commonly applied, there are differences in reference values and physiologic reaction to dynamic tests. However, donkeys seem to suffer from typical equine diseases, such as metabolic syndrome and pituitary pars intermedia dysfunction (PPID). Asinine metabolic syndrome (AMS) comprises obesity, insulin dysregulation, and laminitis. The principles of diagnosis are similar to horses. Donkey-specific reference ranges for insulin and glucose have been evaluated previously. Examinations regarding dynamic testing revealed differences in the intravenous glucose tolerance test and the combined insulin tolerance test compared to horses. The therapy of AMS is based mainly on weight loss and exercise. There are conflicting data regarding the incidence of PPID in donkeys. Laminitis and hypertrichosis were described as the main clinical signs. Species-specific and seasonal reference ranges were defined to diagnose PPID in donkeys. Furthermore, the dexamethasone suppression test, the thyrotropin releasing hormone (TRH) test and the combined dexamethasone suppression/TRH test were evaluated. Pergolide is commonly recommended for treatment.

Keywords: ACTH; PPID; insulin dysregulation; metabolic syndrome.

Figure 1

Hooves of a donkey with signs of chronic laminitis. Note the divergent growth rings.

Figure 2

Obese donkey with a body condition score of 5.

Figure 3

Typical combined glucose insulin test in donkeys compared to horses.

Figure 4

Typical intravenous glucose tolerance test in donkeys compared to horses.