Maybe low T isn't so bad after all. A new study found that testosterone therapies doubled the heart attack risk for men over age 65 after only three months. Heart attack risk also doubled for younger men with a history of heart disease. "This is a warning that testosterone therapy shouldn't be prescribed cavalierly," says Dr. Bradley Anawalt, a testosterone researcher at University of Washington in Seattle. "Men with borderline low testosterone but without testicular or pituitary disease should be very cautious — it is not a magic potion to restore youth, and the risks are unknown."

This and other recent studies have prompted the FDA to take another look at the safety of a number of testosterone-boosting products like AndroGel which, all told, are being taken by some 5.6 million men. "The FDA has not regulated the large promotional campaign for low T which has driven the tremendous surge in testosterone prescription," says Dr. Lisa Schwartz, a professor at the Dartmouth Institute for Health Policy and Clinical Practice. "It should."