Thyroid Hormone-Regulated Genes in the Brain

Thyroid hormone exerts its actions by binding to nuclear receptors and regulating gene expression. Gene expression regulation by thyroid hormone in the brain is highly complex, with thousands of genes under the direct or indirect influence of T3. Adding to the complexity, gene dependence of T3 is age- and region-dependent, with diverse time window sensitivity. The maximal gene expression responses to T3 in rodents extend from the last 2-3 days of fetal life to the end of the first month, peaking around postnatal days 15-21. T3 regulates genes involved in almost all aspects of brain function, from developmental genes to genes involved in metabolic and cell signaling pathways. In most cases, the effect of T3 is to fine-tune the relative abundance of selected gene products at the right time and place, promoting maturational processes during developmental transitions.