Thyroid hormone, brain development, and behavior

Dr. Bjorn Vennstrom and colleagues in Spain and at the Karolinska Institute (Sweden) have identified novel neural functions of thyroid hormone (TH), revealing that it is required during discrete periods of brain development to confer “normal” behavior.

The scientists used transgenic mice heterozygous for a mutant form of the thyroid hormone receptor alpha1 that has about a ten-fold reduced affinity for its natural ligand, TH. They observed that reduced TH signaling during development lead to distinct neurological abnormalities in adulthood: extreme anxiety, reduced memory and locomotor dysfunction. Interestingly, the anxiety and memory impairment could be suppressed through dietary supplementation of the adult mice with TH (supplementation was not effective when administered as a juvenile).

Conversely, the uncoordination could be normalized through TH injections at juvenile (but not adult) stages. “Since most psychiatric diseases are thought to have a polygenic background, these discoveries may have valuable implications for the diagnosis and treatment of certain mood disorders,” explains Dr. Vennstrom.