Abstract

In rats subjected to thyroidectomy there was a two- to fourfold increase in cerebral cortex iodothyronine 5'-deiodinase activity within 24 hours. This increase was prevented by thyroxine replacement. The increased cortical 5'-deiodinase in chronically hypothyroid rats was normalized within 4 hours by a single intravenous injection of triiodothyronine. These results indicate that the adult central nervous system can give a very rapid biochemical response to thyroid hormone.

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