Serum cortisol and thyroid hormone concentrations and survival in foals born from mares with experimentally induced ascending placentitis.
Authors: Müller Vitória, Toribio Ramiro E, Dembek Katarzyna, Moraes Bruna S S, Mousquer Mariana A, Curcio Bruna R, Nogueira Carlos E W
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Cortisol and Thyroid Markers as Prognostic Indicators in Foals Born to Mares with Placentitis When placental infection occurs during pregnancy, the developing foal's endocrine system can suffer lasting consequences that may be detectable at birth. Researchers investigated whether measuring serum cortisol and thyroid hormone concentrations in newborn foals could predict survival outcomes, particularly in animals born to mares with ascending placentitis. Over the first week of life, they tracked 29 foals (5 controls from healthy mares, 14 low-risk and 10 clinically sick foals from mares with experimentally induced placentitis), measuring both total and free T3 and T4 alongside cortisol at multiple timepoints. Non-surviving sick foals demonstrated markedly suppressed thyroid-to-cortisol ratios compared with sick foals that survived: the T3:cortisol ratio was approximately five-fold lower at 12 hours (3.68 versus 18.58), four-fold lower at 24 hours (5.47 versus 23.40), and two-and-a-half-fold lower at 48 hours after birth. Similarly, the T4:cortisol ratio showed five-fold suppression at 12 hours and three-fold suppression at 24 hours in non-survivors. These findings suggest that intrauterine placentitis impairs fetal thyroid development, manifesting as nonthyroidal illness syndrome—and crucially, the degree of this thyroid suppression relative to elevated stress hormones appears predictive of outcome. Practitioners managing neonatal foals suspected of placentitis-related compromise should consider early cortisol and thyroid profiling during the first 48 hours as an
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Practical Takeaways
- •Measure serum T3:cortisol and T4:cortisol ratios within the first 12-48 hours of life in at-risk neonatal foals to identify those with poor prognosis and guide intensive care decisions
- •Foals born to mares with placentitis should be monitored closely for thyroid dysfunction, as this may indicate systemic compromise from in-utero infection
- •Low thyroid hormone to cortisol ratios in the first 2 days of life may warrant more aggressive intervention and closer prognostic assessment in sick neonatal foals
Key Findings
- •Sick non-surviving foals had significantly lower T3:cortisol ratios at 12, 24, and 48 hours of life compared to sick surviving foals (3.68-10.47 vs 18.58-26.6)
- •Sick non-surviving foals had significantly lower T4:cortisol ratios at 12 and 24 hours after birth compared to sick surviving foals (75.12-127.83 vs 414.47-430.87)
- •T3:cortisol and T4:cortisol ratios appear to be reliable prognostic markers for survival in newborn foals affected by placental infection
- •Placental infections from experimentally-induced ascending placentitis impaired fetal thyroid function in affected foals