Effect of thyroxine administration on renal functions in newborn infants with perinatal asphyxia.

The study was undertaken to assess the influence of thyroxine given to improve respiratory adaptation in asphyxiated neonates on the recovery of compromised renal functions. Two groups of infants with perinatal asphyxia were selected for the study. Group I consisted of 8 infants treated conventionally, while Group II included 7 infants who in addition to standard therapy were administered 50 micrograms thyroxine at admission and repeated 24 hours later. Their respective mean gestational ages were 38.7 weeks (range: 34-42 weeks) and 37.4 weeks (range: 34-41 weeks). The studies were performed on days 1, 7 and 14 and the results compared to those obtained in 13 healthy neonates with the gestational age of 39.2 weeks (range: 38-41 weeks) (Group III). Asphyxiated neonates had significantly higher plasma uric acid, xanthine, hypoxanthine and creatinine levels (p < 0.05), while their GFR proved to be markedly reduced (p < 0.01) when compared to the values of healthy controls. Moreover, there was a significant elevation of urinary excretion of NAGA (p < 0.001), urine osmolality (p < 0.05), PENa, FECa, RFI (p < 0.05) in infants presenting with perinatal asphyxia. Renal tubular responsiveness to aldosterone measured as TTKG was also found to be depressed (p < 0.025). In response to thyroxine therapy renal functional recovery appeared to be accelerated as indicated by the lower plasma creatinine level, lower rate of fractional electrolyte and urinary NAGA excretion and improved reactivity to aldosterone on days 7 and/or 14 as compared to those obtained in neonates presenting with asphyxia but without thyroxine therapy. The results seem to suggest that thyroid hormones may have an important role in the recovery of renal functions in newborn infants suffering from perinatal asphyxia.