Last Updated: 2007-09-24 17:00:15 -0400 (Reuters Health)

NEW YORK (Reuters Health) – The novel thyroxine derivatives, thyronamine and 3-iodothyronamine, induce transient hypothermia and marked neuroprotection against stroke injury in a murine model, researchers report in the September issue of Stroke.

Dr. Mary P. Stenzel-Poore and colleagues at Oregon Health and Science University, Portland recently found that these agents lower body temperature in rodents. According to their report, the natural thyroxine derivatives cause "a temporary reduction in spontaneous activity without other discernible behavioral changes."

To test whether the resultant hypothermia might be protective against brain injury in stroke, the researchers tested the agents 1 hour and 2 days before experimental stroke in a mouse model of focal ischemia.

Administration of the thyroxine derivatives reduced body temperature from 37 degrees C to 31 degrees C, and animals given the agents after the ischemic period had significantly smaller infarcts than did controls. In addition, mice preconditioned with thyronamine showed significantly smaller infarcts than controls.

In vitro studies showed no neuroprotective effect of thyronamine or 3-iodothyronamine against ischemia.

"Thyronamines offer a novel therapeutic approach for the treatment of individuals at risk of brain ischemia, such as those undergoing coronary artery bypass surgery," Dr. Stenzel-Poore told Reuters Health. "These compounds are particularly promising because they exist as naturally occurring metabolites in the body."

Stroke 2007;38:2569-2576.