Vasopressin stimulation testing in hospitalized foals

Area of Science:

• Veterinary Medicine
• Endocrinology
• Equine Health

Background:

• Hypothalamic-pituitary-adrenal gland axis (HPAA) dysfunction can compromise foal survival.
• The arginine vasopressin (AVP) stimulation test is a diagnostic tool for HPAA dysfunction.

Purpose of the Study:

• To evaluate adrenocorticotropic hormone (ACTH) and cortisol response to AVP stimulation in hospitalized foals.
• To compare AVP test results between healthy, septic, and sick non-septic (SNS) foals.
• To correlate HPAA function with disease severity in foals.

Main Methods:

• Prospective, observational case-control study involving 15 healthy and 45 hospitalized foals (19 septic, 26 SNS).
• Administration of AVP (5 IU) with serial measurements of corticotropin-releasing hormone, ACTH, and cortisol at 0, 15, 30, 60, and 90 minutes.
• Calculation of ACTH and cortisol fold increase at 15 and 30 minutes post-AVP administration.

Main Results:

• All foal groups showed increased ACTH and cortisol concentrations 15 and 30 minutes after AVP administration (P < .05).
• Septic and SNS foals exhibited lower ACTH concentrations at 15 minutes compared to healthy foals (P < .05).
• Fold increase in ACTH was significantly lower in septic foals versus SNS and healthy foals (P < .01).
• Fold increase in cortisol was lower in septic foals compared to healthy foals (P < .05).

Conclusions:

• HPAA dysfunction, indicated by reduced ACTH and cortisol response to AVP, is associated with disease severity in foals.
• The AVP stimulation test can identify HPAA dysfunction in ill foals.
• This diagnostic tool may assist in therapeutic decisions for hospitalized foals.