New research suggests that testosterone treatment could prevent or delay the onset of Alzheimer's disease in aging men and women. According to findings detailed in a report released yesterday by the Proceedings of the National Academy of Sciences, doses of the hormone, given alone or in combination with estrogen, staved off a key chemical aberration characteristic of the disease in rats.

Women carry a higher risk for Alzheimer's than do men, a difference that scientists have attributed to the decline of estrogen (which is known for its neuroprotective effects) after menopause. As a result, much research has focused on the potential benefits of estrogen in preventing or treating the disease. Sozos Papasozomenos and Alikunju Shanavas of the University of Texas-Houston thus decided to turn their attention to the male hormone testosterone. The researchers focused on a hallmark of the disease in which a brain protein called tau forms snarls of filaments, so-called neurofibrillary tangles, through a chemical reaction known as hyperphosphorylation. As it turns out, exposing rats to high temperatures triggers this same reaction. But the researchers found that treating the rats with testosterone or a combination of testosterone and estrogen prior to heat exposure prevented the hyperphosphorylation of tau by blocking the overactivation of an enzyme involved in the process.

Considering that estrogen counteracts some of the effects of androgens like testosterone, Papasozomenos and Shanavas note, estrogen alone could prove detrimental rather than protective against Alzheimer's. They assert, however, that their research results indicate that testosterone given alone to aging men or along with estrogen to postmenopausal women would probably aid prevention or treatment of the disease.