Researchers have found that an arginine vasopressin stimulation (AVP) test offers a reliable way to assess endocrine function in sick foals. The work, published in the Journal of Veterinary Internal Medicine, could lead to faster identification and treatment, improving survival rates for foals with hypothalamic-pituitary-adrenal gland axis (HPAA) dysfunction.
Proper function of the endocrine system—responsible for releasing hormones into the bloodstream—is critical to the survival of newborn foals. Unfortunately, these foals are at the greatest risk of hormonal dysfunction because their endocrine systems are not fully developed at birth. If a newborn foal becomes ill and its endocrine system doesn't respond appropriately, its chances of survival decrease.
"The HPAA in particular is important for foal survival," says Katarzyna Dembek, associate professor of equine medicine at North Carolina State University. "That's because when a foal is sick, it stimulates the HPAA to release a cocktail of hormones: adrenocorticotropic hormone (ACTH); corticotropin-releasing hormone (CRH); arginine-vasopressin (AVP); and cortisol, the stress hormone, which helps the body survive critical illnesses."
"ACTH stimulation—which tells the adrenal cortex to produce cortisol—is the current gold-standard method for testing endocrine function in horses, although studies have shown poor reliability and performance in critically ill foals," Dembek says.
"Arginine vasopressin (AVP) stimulates ACTH release, and it has the additional advantage of being the primary adrenocorticotropin-releasing hormone in horses. We wanted to determine whether AVP stimulation would be useful for testing endocrine function in foals."
Dembek and the research team looked at a cohort of 60 newborn (less than 1-week-old) foals: 15 healthy, 19 septic and 26 sick but not septic. They administered AVP and then measured ACTH and cortisol levels in the blood at 15-, 30-, 60- and 90-minute intervals following administration.
They found that ACTH and cortisol concentrations increased in all groups 15 to 30 minutes after AVP administration. In septic foals, both ACTH and cortisol levels were lower than in the other groups, and they didn't increase as rapidly.
The researchers found the results promising not only for diagnosing HPAA dysfunction but also as a potential indicator of prematurity in foals.
"This study shows that AVP stimulation is promising in determining how sick a foal may be and could aid in early intervention, particularly in foals without many clinical signs of illness," Dembek says. "And in foals where we saw no real change from baseline, the lack of cortisol production could indicate that they are premature."
Early diagnosis of HPAA dysfunction and lack of cortisol enables the use of hydrocortisone therapy in sick foals to enhance their chances of survival. A similar approach—currently being studied by Dembek—can also be applied to critically ill adult horses.
"AVP is widely available, compatible with horses and largely affordable," Dembek says. "Its use in diagnosing HPAA dysfunction warrants further exploration."
More information
Myriah Albrecht et al, Vasopressin stimulation testing in hospitalized foals, Journal of Veterinary Internal Medicine (2026). DOI: 10.1093/jvimsj/aalag149
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Citation: Researchers identify useful tool for diagnosing endocrine dysfunction in sick foals (2026, July 27) retrieved 27 July 2026 from https://phys.org/news/2026-07-tool-endocrine-dysfunction-sick-foals.html
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