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Journal of veterinary internal medicine2026; 40(4); aalag149; doi: 10.1093/jvimsj/aalag149

Vasopressin stimulation testing in hospitalized foals.

Abstract: Hypothalamic-pituitary-adrenal gland axis (HPAA) dysfunction impairs survival and can be diagnosed with an arginine vasopressin (AVP) stimulation test. Objective: Adrenocorticotropic hormone (ACTH) and cortisol response to an AVP stimulation test will be attenuated in hospitalized foals compared to healthy foals and associated with severity of disease. Methods: Fifteen healthy and 45 hospitalized foals: 19 septic, 26 sick non-septic (SNS). Methods: A prospective, observational case-control design was utilized to assess HPAA function and compare corticotropin-releasing hormone, ACTH, and cortisol concentrations at 0, 15, 30, 60, and 90 min after administration of AVP (5 IU). Adrenocorticotropic hormone and cortisol fold increase were calculated at 15 and 30 min compared to baseline. Results: Adrenocorticotropic hormone and cortisol concentrations increased at 15 and 30 min after AVP administration in all groups (P < .05). Adrenocorticotropic hormone concentration was lower in septic (112; 95% CI, 86.3-181.8 pg/mL) and SNS (102; 95% CI, 82.8-150 pg/mL) compared to healthy foals (179; 95% CI, 135.6-275.8 pg/mL) 15 min after AVP administration (P < .05). Fold increase in ACTH was lower in septic (3.3; 95% CI, 2.3-5.6) compared to SNS (3.7; 95% CI, 3.5-6.1) and healthy foals (7; 95% CI, 5.7-9.5; P < .01). Fold increase in cortisol was lower in septic (2; 95% CI, 1.8-8.3) compared to healthy foals (4.3; 95% CI, 2.8-9.4; P < .05). Conclusions: Hypothalamic-pituitary-adrenal gland axis dysfunction, evidenced by ACTH and cortisol responses to an AVP stimulation test, appears linked to disease severity and is a complication of illness. An AVP stimulation test might help guide therapy in ill foals.
© The Author(s) 2026. Published by Oxford University Press on behalf of the American College of Veterinary Internal Medicine.
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Publication Date: 2026-07-23 PubMed ID: 42492062PubMed Central: PMC13395086DOI: 10.1093/jvimsj/aalag149Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated how hospitalized foals respond to arginine vasopressin (AVP) stimulation in terms of hormone levels related to stress and illness (ACTH and cortisol), comparing sick and healthy foals.
  • The findings suggest that foals with severe illness show impaired hormone responses, indicating dysfunction of the hypothalamic-pituitary-adrenal gland axis (HPAA), which could help inform treatment decisions.

Background and Objective

  • The hypothalamic-pituitary-adrenal gland axis (HPAA) is crucial for regulating stress responses and survival during illness.
  • Dysfunction of this axis can worsen outcomes in sick animals.
  • Arginine vasopressin (AVP) stimulation tests measure HPAA function by triggering the release of adrenocorticotropic hormone (ACTH) and cortisol, key hormones in the stress response.
  • The study aimed to compare ACTH and cortisol responses to AVP between hospitalized foals (both septic and non-septic sick) and healthy foals, hypothesizing that the hormone responses would be weaker in the hospitalized groups and relate to illness severity.

Methods

  • A prospective, observational case-control design was used.
  • Sixty foals were divided into three groups:
    • 15 healthy foals.
    • 19 septic (severely ill with infection).
    • 26 sick non-septic (SNS) foals (ill but no infection).
  • Each foal received an intravenous dose of AVP (5 IU).
  • Blood samples were collected at baseline (0 min) and at 15, 30, 60, and 90 minutes post-administration to measure concentrations of:
    • Corticotropin-releasing hormone (CRH).
    • Adrenocorticotropic hormone (ACTH).
    • Cortisol.
  • Fold increases in ACTH and cortisol were calculated at 15 and 30 minutes compared to baseline values.

Results

  • All groups showed an increase in ACTH and cortisol at 15 and 30 minutes after AVP.
  • The magnitude of these increases differed significantly among groups:
    • ACTH concentrations at 15 minutes:
      • Septic foals: median 112 pg/mL (95% CI: 86.3–181.8)
      • Sick non-septic foals: median 102 pg/mL (95% CI: 82.8–150)
      • Healthy foals: median 179 pg/mL (95% CI: 135.6–275.8)
    • Fold increase in ACTH at 15 and 30 minutes:
      • Septic foals: 3.3 (95% CI: 2.3–5.6)
      • Sick non-septic foals: 3.7 (95% CI: 3.5–6.1)
      • Healthy foals: 7 (95% CI: 5.7–9.5)
    • Fold increase in cortisol:
      • Septic foals: 2 (95% CI: 1.8–8.3)
      • Healthy foals: 4.3 (95% CI: 2.8–9.4)
  • Statistical analysis showed significant attenuation of both ACTH and cortisol responses in septic foals compared to healthy foals.
  • These findings indicate a diminished HPAA response to AVP stimulation in severely ill foals.

Conclusions and Implications

  • HPAA dysfunction, as evidenced by reduced ACTH and cortisol responses to AVP, correlates with severity of illness in hospitalized foals.
  • The AVP stimulation test effectively identifies impaired stress hormone responses in sick foals.
  • Such testing might be clinically useful to:
    • Assess adrenal function in ill foals.
    • Guide therapeutic interventions based on hormone responsiveness.
    • Potentially improve survival by tailoring treatments to the foals’ hormonal capacity to cope with illness.
  • Further research could explore how AVP testing influences clinical outcomes and therapeutic strategies.

Cite This Article

APA
Albrecht M, Perez J, Wong D, Browne N, Burns T, Stevens ME, Dembek K. (2026). Vasopressin stimulation testing in hospitalized foals. J Vet Intern Med, 40(4), aalag149. https://doi.org/10.1093/jvimsj/aalag149

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: England
Language: English
Volume: 40
Issue: 4
PII: aalag149

Researcher Affiliations

Albrecht, Myriah
  • Department of Clinical Sciences, The Ohio State University, Columbus, OH, United States.
  • Internal Medicine, Hagyard Equine Medical Institute, Lexington, KY, United States.
Perez, Javier
  • Veterinary Associates Equine, Auckland, New Zealand.
Wong, David
  • Department of Clinical Sciences, Iowa State University, Ames, IA, United States.
Browne, Nimet
  • Internal Medicine, Hagyard Equine Medical Institute, Lexington, KY, United States.
Burns, Teresa
  • Department of Clinical Sciences, The Ohio State University, Columbus, OH, United States.
Stevens, Maddie Edwards
  • Oklahoma City Equine Clinic, Oklahoma City, OK, United States.
Dembek, Katarzyna
  • Department of Clinical Sciences, North Carolina State University, Raleigh, NC, United States.

MeSH Terms

  • Animals
  • Horses
  • Adrenocorticotropic Hormone / blood
  • Horse Diseases / diagnosis
  • Horse Diseases / blood
  • Hydrocortisone / blood
  • Arginine Vasopressin / pharmacology
  • Case-Control Studies
  • Corticotropin-Releasing Hormone / blood
  • Female
  • Male
  • Pituitary-Adrenal System / physiopathology
  • Hypothalamo-Hypophyseal System / physiopathology
  • Hypothalamo-Hypophyseal System / drug effects
  • Sepsis / veterinary
  • Sepsis / diagnosis
  • Sepsis / blood
  • Prospective Studies

Grant Funding

  • Morris Animal Foundation

Conflict of Interest Statement

The authors declare no conflicts of interest.

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