Pituitary pars intermedia dysfunction (equine Cushing’s disease) in a Thoroughbred stallion: a single report.

This study focuses on a rare case of Equine pituitary pars intermedia dysfunction (PPID), also known as Cushing’s disease, in a 21-year-old Thoroughbred stallion. The stallion displayed typical PPID symptoms including excessive hair growth (hirsutism) and late shedding of fur (delayed molting), but its reproductive activities appeared unaffected.

Study Details

• The research describes a single case study of PPID in a Thoroughbred stallion, a subject group that has not been heavily explored in prior studies.
• PPID is a condition that usually manifests in older horses with symptoms such as excessive thirst and urination (polydipsia, polyuria), unregulated body weight (weight loss), inflammations in the feet (laminitis) and reproductive disorders. In the highlighted case, the stallion was affected with hirsutism and delayed molting.
• Despite the diagnosis, the reproductive capacity of the stallion, as judged by semen quality and sexual desire, did not appear to be affected. This is an unusual finding, providing an interesting anomaly in the study of PPID.

Examination and Diagnosis

• The horse’s condition was diagnosed as PPID upon administering a dexamethasone suppression test and through measuring plasma levels of adrenocorticotropic hormone, both of which are standard procedures used in identifying this disease.
• The horse was subsequently treated with pergolide mesylate, a common course of treatment for PPID.

Autopsy Findings

• Unfortunately, the patient died during the course of the study due to a fracture in the humerus bone. An autopsy was performed post-mortem which confirmed the presence of a pituitary adenoma, a benign tumor that is commonly associated with PPID.
• Critical to the findings of this study, the autopsy did not reveal any pathology in the testicles, which further suggests that the stallion’s reproductive activity was not influenced by the disease. This challenges the common understanding of PPID, providing a potential avenue for future research.