Euthyroid status is essential for the perinatal increase in thermogenin mRNA in brown adipose tissue of rat pups

The amount of mRNA coding for the brown-fat specific, uncoupling protein thermogenin was followed perinatally in fetuses and newborns from normal and hypothyroid rat dams. Although the growth of the fetuses and newborns was normal in the hypothyroid group, they had a lower amount of thermogenin mRNA already in-utero, and the dramatic postnatal increase in thermogenin mRNA was nearly completely abolished. It is concluded that the euthyroid state is essential for the regulation of the expression of the thermogenin gene.