| The recognition of stereospecific binding sites for triiodothyronine in liver and kidney nuclei in our laboratory in 1972 was followed shortly thereafter by the discovery of similar sites in other tissues, including brain. These observations stimulated a series of studies which have provided convincing evidence that T3 receptors are the points of initiation of those thyroid hormone-stimulated processes which contribute to brain development. They also raised the possibility that such receptors initiate some or all of the effects of thyroid hormone in the adult brain. Observations in our laboratory and that of Dr. Morreale de Escobar indicated the presence of thyroid hormone receptors in rat fetus and both laboratories documented a surge in receptor concentration one to two days after birth. The rise in brain receptor content preceded the rise in the serum T3 concentration. The presence of both T3 receptors and transplacentally transmitted thyroid hormone in the fetus raised the possibility that thyroid hormone could influence brain maturation in the prenatal as well as in the postnatal state. Further, the postnatal surge in serum thyroid hormone and thyroid hormone receptors appeared to trigger the well-recognized anatomic changes produced by thyroid hormone during the first 3 weeks of neonatal life. |
