GELLERMAN: Just ahead: from a trickle to a turbulence. Getting the Colorado River to flow again to the Gulf of California. First, this Environmental Health Note from Diane Toomey.

TOOMEY: Commercials abound nowadays touting the benefits of testosterone replacement therapy for men. But there’s no clear scientific information about either the benefits – or the risks--of these treatments. The Institute of Medicine recently announced that rigorous clinical trials should be done on testosterone use, but initially on a small scale. This recommendation was made after a request to investigate the phenomenon came from the National Institute of Aging, sparked by the growing trend of older men using this therapy as levels of their natural testosterone decrease.

According to the Institute of Medicine, the limited studies that have been done on testosterone therapy didn’t show any major side effects. But there isn’t enough evidence to say definitively that the treatments are safe, since research subjects haven’t been followed long enough. So the Institute recommends limited tests that follow men for up to two years to see if there are benefits in terms of improved strength, sexual function, cognitive function, and general well-being from testosterone replacement therapy, all claims made by its advocates.

If benefits do exist, then the panel recommends a long-term study to see these higher levels of testosterone increase chances of developing prostate cancer.

That’s this week’s Health Note, I’ve Diane Toomey.

GELLERMAN: And you're listening to Living on Earth.