Thyroid hormone plays a key role in regulating a range of physiologic functions, including metabolism, temperature, heart rate, and growth. It accomplishes this impressive array of activities by interacting with almost every organ system in the body. Yet despite a long history of research on how thyroid hormone influences different organs, its effects on arguably the most crucial organ -; the brain -; have remained shrouded in mystery.
Now, scientists at Harvard Medical School have gained new insights into thyroid hormone's effects on the brain. The work, conducted in mice and published on August 22nd, 2024 in Cell , shows that thyroid hormone changes the wiring of brain circuits in a manner that drives animals to engage in exploratory behavior. By simultaneously changing brain wiring and altering metabolic rate, the researchers concluded that thyroid hormone coordinates the brain and body to produce exploratory behavior when it is most needed -; for example, during seasons when animals need to find mates or stockpile resources.
It's well known that thyroid hormone modulates metabolism, and now we've shown that it also modulates exploratory behaviors through direct action on the brain." Daniel Hochbaum, Study Lead Author and Research Fellow, Neurobiology, Blavatnik Institute, Harvard Medical School The findings also help elucidate how low levels of the hormone could lead to depressive states marked by a low desire to explore, while too much could precipitate manic states char.