Lamellar pathology in horses with pituitary pars intermedia dysfunction

Area of Science:

• Equine pathology
• Veterinary endocrinology
• Histomorphometry

Background:

• Hoof lamellar pathology in horses with pituitary pars intermedia dysfunction (PPID) has not been previously described.
• PPID is a common endocrine disorder in aged horses.

Purpose of the Study:

• To describe the histomorphometry and pathological lesions in hoof lamellar tissue of horses with PPID.
• To compare findings in PPID horses with and without concurrent laminitis to age-matched controls.
• To investigate the association between PPID, laminitis, and metabolic parameters like hyperinsulinaemia.

Main Methods:

• A prospective case-control study design was employed.
• Histological sections of hoof lamellae were obtained post-mortem from PPID-affected horses (with and without laminitis) and control horses.
• Image analysis was used to measure lamellar dimensions, and a veterinary pathologist assessed lamellar morphology and pathology. Fasting serum insulin, plasma ACTH, and blood glucose were measured.

Main Results:

• Horses with PPID and laminitis exhibited fasting hyperinsulinaemia, while PPID horses without laminitis did not.
• Lamellar pathology in PPID horses with laminitis was variable and included increased lamellar size, abnormal keratinisation, epidermal bridging, and cell death.
• The lamellae of PPID horses without laminitis appeared normal compared to controls.

Conclusions:

• Hyperinsulinaemia, rather than PPID itself, appears to be associated with lamellar morphological alterations and pathology consistent with laminitis.
• The findings suggest a potential link between metabolic disturbances in PPID and the development of laminitis.