Evaluation of dynamic testing for pituitary pars intermedia dysfunction diagnosis in donkeys

Area of Science:

• Veterinary Endocrinology
• Equine and Donkey Health
• Animal Diagnostics

Background:

• Endocrine disorders, including pituitary pars intermedia dysfunction (PPID), are prevalent in donkeys.
• PPID is suspected to be common in aging donkeys, but diagnostic testing protocols are not well-established for this species.
• Existing diagnostic guidelines for PPID in horses have not been previously evaluated in donkeys.

Purpose of the Study:

• To assess the applicability of established equine diagnostic guidelines for PPID in donkeys.
• To compare the efficacy of dynamic endocrine function tests for PPID diagnosis in donkeys.

Main Methods:

• A prospective experimental study involving eighty donkeys initially evaluated for PPID suspicion.
• Six donkeys meeting inclusion criteria underwent dexamethasone suppression test (DST), thyrotropin-releasing hormone (TRH) stimulation test, and a combined DST-TRH challenge.
• Tests were interpreted using criteria established for PPID diagnosis in horses.

Main Results:

• The TRH stimulation test successfully diagnosed PPID in all six donkeys (6/6).
• The DST and combined DST-TRH challenge yielded inconclusive and conflicting results, failing to consistently identify PPID.
• Basal cortisol concentrations did not correlate with PPID suspicion.

Conclusions:

• The TRH stimulation test, alongside baseline ACTH measurement, shows promise for diagnosing PPID in donkeys.
• Further research is warranted to investigate the influence of seasonal and geographical factors on baseline ACTH and TRH test responses in donkeys.
• This study provides initial evidence supporting the use of equine PPID diagnostic protocols in donkeys, with TRH stimulation being a key component.