Can Endocrine Dysfunction Be Reliably Tested in Aged Horses That Are Experiencing Pain?

Area of Science:

• Veterinary Endocrinology
• Equine Internal Medicine

Background:

• Pituitary pars intermedia dysfunction (PPID) diagnosis in horses can be complicated by concurrent conditions.
• Pain can influence hormonal responses, potentially affecting diagnostic accuracy for endocrine disorders.

Purpose of the Study:

• To assess the impact of treated pain (low to moderate intensity) on basal adrenocorticotropic hormone (ACTH) and cortisol concentrations in horses.
• To evaluate the influence of treated pain on the thyrotropin-releasing hormone (TRH) stimulation test's efficacy in diagnosing PPID.

Main Methods:

• Fifteen horses with treated pain (colic, laminitis, orthopedic issues) were studied, serving as their own controls when pain-free.
• A composite pain scale assessed pain intensity across different disease groups.
• Basal ACTH and cortisol levels were measured, followed by assessment after intravenous TRH administration.

Main Results:

• No significant differences were observed in basal or TRH-stimulated ACTH and cortisol concentrations between pain and control states.
• Pain did not lead to a marked increase in ACTH, which could cause false positives for PPID.
• A slight, statistically unconfirmed, increase in ACTH was noted 30 minutes post-TRH in the pain group.

Conclusions:

• Measuring basal ACTH and performing the TRH stimulation test appear reliable for diagnosing PPID in horses with low to moderate pain.
• Treated pain does not significantly interfere with the hormonal parameters assessed in this study for PPID diagnosis.