Thyroid hormones concentrations in foals affected by Perinatal Ashyxia Syndrome

The purpose of this study was the evaluation of total plasma thyroid hormones (TH) (T3 and T4) concentration in foals affected by Perinatal Asphyxia Syndrome (PAS) compared to healthy foals. Twenty-one healthy and 24 PAS foals £7 days-old were included in this study. Jugular blood samples were collected at birth/admission and every 24 h for 7 days (T0–T7). TH concentrations were analyzed by radioimmunoassay (RIA). Statistical analysis was carried out to evaluate: the time-dependent changes in TH concentrations in healthy and PAS foals, the comparison in TH concentration at admission between surviving and nonsurviving foals, and between healthy and PAS foals evaluated for age at admission. In both groups, T3 concentration significantly decreased at T5 compared to T1 (p< 0.05), and T4 plasma levels significantly decreased from T0 (p< 0.01). No differences were found in T3 and T4 concentrations at admission between surviving (n.20) and nonsurviving (n.4) foals. Statistical comparison between healthy and PAS foals divided in age groups showed a significantly lower T3 and T4 concentration at T0 in PAS foals (p< 0.01). In conclusion, the lower TH concentrations in PAS foals could be due to an ‘euthyroid sick syndrome’, that represents an adaptive response to reduce metabolic rate and to prevent organ failure, as reported in human neonates. TH concentration showed no prognostic value, maybe due to the small number of nonsurviving foals in this study.