By MARK ROTH, Pittsburgh Post-Gazette

As men age, their testosterone levels naturally drop.

But for some men, the male sex hormone may sink so low that they not only lose all interest in sex, but suffer more falls, have memory problems and experience anemia.

A new national study will explore whether applying testosterone gel to the abdomen, torso or upper arms can reverse those effects.

In the last 50 years, circumcision in America has been on a steady decline, and is now done on only 55 percent of baby boys.

But that may change if two major health groups adopt new recommendations based on striking results from African studies that show circumcised men are much less likely to get HIV.

A black hole walks into a bar and says, "Hey, where'd everybody go?"

That old joke captures the essence of what most people believe about black holes -- places in the universe so dense that they suck in all matter and light, letting nothing escape.

After hearing the warnings about the mercury we ingest when eating fish and how toxic heavy metals are, it might seem like a bad idea to use mercury in vaccines that are injected into the human body.

But scientists say that the mercury used with some vaccines -- known as ethyl mercury or thimerosal -- is much different than the methyl mercury that comes from fish.

Dr. Anne Germain is biased toward sleep.
As a sleep researcher at the University of Pittsburgh, she naturally focuses on the somnambulant side of the daily cycle.
But she also believes there is growing evidence that sleep problems are actually the cause of many psychological and physical illnesses, rather than a side effect of them.

Experts do not believe the recent spate of suicides by top businessmen, including the death of Freddie Mac's acting chief financial officer, is the beginning of a wave of such tragedies because of economic stresses.
There are two things to keep in mind about such deaths, notes one expert.

In a critical moment of the Academy Award-winning film, "The Best Years of Our Lives," amputee Homer Parrish reaches for a wedding ring with his hook prosthetic, grasps it and then delicately slides it onto the finger of his childhood sweetheart, Wilma Cameron.

The horrors of war have often led to medical benefits in peacetime.
The Civil War spread the use of anesthesia. World War II helped to start the antibiotics revolution. And now, the Iraq War and its deadly roadside bombs are advancing the development of prosthetics for those who have lost limbs.

In some ways, Von Ferber and Kirk Arnold are mirror images of each other.
Both are big, physically active men. Both love to ride motorcycles. And both are missing their right hands and use prosthetics as substitutes.

In the past month alone, eight multiple-shooting incidents have occurred in the United States and Europe, leaving 70 dead, including three Pittsburgh police officers killed April 4.
In the criminology trade, they are known as mass murders, and they usually share several common traits, experts say.