The hypothalamic-pituitary-adrenal axis response to ovine corticotropin-releasing-hormone stimulation tests in healthy and hospitalized foals.
Authors: Johnson Katheryn, Peterson Jackie, Kopper Jamie, Dembek Katarzyna
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: CRH Stimulation Testing in Neonatal Foals Sepsis and critical illness can compromise the hypothalamic-pituitary-adrenocortical (HPAA) axis function in foals, yet clinicians currently lack reliable diagnostic tools to assess this responsiveness in sick neonates. Johnson and colleagues evaluated how healthy (n=14) and hospitalised (n=15) foals aged less than seven days responded to three different intravenous doses of ovine corticotropin-releasing hormone (oCRH)—0.1, 0.3, and 1 µg/kg—measuring cortisol, ACTH, endogenous CRH, and arginine vasopressin at baseline and up to 90 minutes post-administration. Across both groups, cortisol concentrations rose significantly from baseline within 15 minutes at lower doses and by 30–60 minutes at the highest dose; ACTH responses were more pronounced in hospitalised foals, particularly with the 1 µg/kg dose. The 1 µg/kg oCRH dose produced the most robust and consistent hormonal changes in both healthy and sick foals, suggesting it is the optimal stimulation strength for assessing HPAA competence in neonatal populations. For equine practitioners managing critically ill foals, this research establishes a practical diagnostic protocol that could help identify HPAA dysfunction and potentially guide prognostic assessment and therapeutic decisions in septic cases.
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Practical Takeaways
- •The 1 μg/kg dose of ovine CRH is the recommended dose for clinical assessment of adrenal function in neonatal foals, providing the clearest hormonal response
- •CRH stimulation testing can differentiate HPAA response patterns between healthy and hospitalized foals, potentially aiding in diagnosis of critical illness-related adrenal insufficiency
- •Blood samples should be collected at 15-30 minute intervals post-CRH administration to capture peak cortisol and ACTH responses in clinical practice
Key Findings
- •Cortisol, ACTH, and endogenous CRH concentrations increased in response to all doses of ovine CRH (0.1, 0.3, and 1 μg/kg) in both healthy and hospitalized foals
- •The 1 μg/kg dose of oCRH produced significantly higher delta cortisol, ACTH, and eCRH responses at 0-30 minutes compared to 0.1 μg/kg in healthy foals
- •ACTH response in hospitalized foals was significantly greater at 15 minutes with 0.1 μg/kg and at 30 minutes with 1 μg/kg oCRH
- •One microgram per kilogram of oCRH appears optimal for assessing HPAA function in both healthy and hospitalized foals less than 7 days of age