Abstract
We have reported data in the human newborn suggesting that the early TSH surge and subsequent hyperthyroid state is due to extrauterine cooling. We now report further studies of this phenomenon in the newborn sheep. Uterotomies were performed on 8 pregnant ewes at term. Three lambs were delivered into room air (21-22° C), five were delivered into 40° C water bath and kept there for 60 min. with cord intact. They were then exposed to room air for an additional 60 min. Rectal and skin temperatures, pulse and blood pressure were monitored serially. T4 and T3 were determined in serum by RIA. Base line T4 values were similar in both groups and did not change significantly during the studies. Mean T3 levels, initially similar in both groups, increased 300% by 60 min. and 672% (p < 0.01) by 120 min. of exposure to room air; mean values in water bath fetuses did not change in or out of the bath. Three/3 exposed fetuses survived and 3/5 of the water bath fetuses died with hypothermia when exposed to room air. The data indicate that neonatal thyroidal hyperactivity is associated with extrauterine cooling but that other factors associated with initial extrauterine exposure must be involved. The T3 response may be important to survival.
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Sack, J., Beaudry, M., Delamater, P. et al. THE MECHANISMS OF NEONATAL THYROIDAL HYPERACTIVITY IN THE NEWBORN SHEEP. Pediatr Res 8, 374 (1974). https://doi.org/10.1203/00006450-197404000-00205
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DOI: https://doi.org/10.1203/00006450-197404000-00205
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