THE EVIDENCE IS PRETTY SOLID IN FAVOR: Is testosterone therapy safe and effective? What we know. I love this:

Testosterone’s reputation has had its ups and downs since the hormone was first synthesized in the 1930s. After an initial golden period, in which it was described as “one of the most potent drugs recently introduced to medicine,” the therapy fell out of favour for fear that it could cause cancer. This idea originated from the work of urologist Charles Huggins who, in 1941, found that prostate cancer depends on testosterone and that lowering the hormone levels caused tumours to shrink. It was a groundbreaking discovery for which he was awarded a share in the Nobel Prize in Physiology or Medicine in 1966.

Morgentaler says that when he was training as a urologist in the 1980s, there was a widespread belief, based on Huggins’s findings, that testosterone therapy could promote prostate cancer. Despite the presumed risks, he says he still thought that the hormone could help some of his patients who had low testosterone and sexual problems. So, he started treating them while monitoring them closely.

They didn’t get cancer, Morgentaler says, and they benefited from the treatment greatly. Some of his clinical findings — along with the revelation that Huggins’s most dire warnings about the hormone causing cancer were based on observations of a single person — helped to clear the way for renewed interest in testosterone therapy.

Sample size: One. So much received medical wisdom comes from this sort of thing.