It's something that men generally think of as a woman's problem. Night sweats, mood swings, hot flashes low libido and exhaustion are on the list of symptoms that can begin years before a woman actually stops having a period.
So Michael Andruzzi, a trim and fit 40-year-old Chicagoan never considered that anything like that might be happening to him.
"I would wake up have as much caffeine as I could possibly take.. and then I would fall right back to sleep," he recalls. "I was cranky, irritable and had the mood swings."
Thinking there was nothing to do about it, he says he gritted his teeth and just lived with it. But then six years ago, he went to Northwestern doctor Robert Brannigan for a different complaint.
And when the urologist started getting a full medical history, and heard the list of symptoms: he immediately checked Andruzzi's testosterone levels.
Andruzzi said the levels came back shockingly low, and even more surprising was that Dr . Brannigan told him he was in andropause, or the male version of menopause.
"I had no idea, " Andruzzi said. "I was completely in the dark."
But low testosterone is a component of aging, Dr. Brannigan says.
"It's normal for men to have a decrease of one to two percent in their testosterone levels as they go through life, so the changes can be gradual in terms of onset of symptoms," he explained.
It's so gradual that many men never feel the effects of those dropping testosterone levels. In Andruzzi's case, it was the exact opposite. He felt those effects at an unusually early age.
Either way, experts increasingly believe the condition is underdiagnosed. Sometimes men slip into this exhausted, irritable state without realizing it, which is why doctors say it's often wives or partners who are the first to point it out.
As for Andruzzi, he said he's telling the guys now because his feeling of wellneess is "fantastic" and he says there's an "incredible" difference.
That difference includes twice-monthly testosterone shots, something his wife, Julie, is quick to remind him about if "there are a couple of days when he gets cranky or grumpy."
Of course, it's a treatment that won't be prescribed for every man with low testosterone. For example, doctors say it wouldn't be prescribed for prostate cancer patients, and there are other groups of men who might face a higher risk of cardiovascular problems.
But for Andruzzi, the shots and the regular doctor's visits to monitor for side effects are easy whenever he thinks of the way he used to feel.
"It's like I'm a different person," he says.