HORMONAL REGULATION OF BRAIN DEVELOPMENT .3. EFFECTS OF TRIIODOTHYRONINE AND GROWTH HORMONE ON BIOCHEMICAL CHANGES IN CEREBRAL CORTEX AND CEREBELLUM OF NEONATALLY THYROIDECTOMIZED RATS

The effects of l-triiodothyronine and bovine growth hormone, administered to neonatally thyroidectomized rats, have been studied in connection with the changes in nucleic acid content and enzymic activities of the cerebral cortex and cerebellum. When administered from the 10th day of age, both triiodothyronine and bovine growth hormone were effective in correcting the alterations produced by neonatal thyroidectomy. On the contrary, when the beginning of treatments were delayed until the 15th day of age, triiodothyronine and/or bovine growth hormone showed no restoring effect. The finding that bovine growth hormone was as effective as triiodothyronine raises the question of whether the effects of early thyroid dysfunction on cerebral development reflect a direct action of thyroid hormone on this process or whether they are indirectly mediated. © 1969.