If you bring up the topic of low testosterone (commonly known as low T), you'll likely hear a wide range of theories and opinions.

Some believe low T is just a natural part of aging for men and, therefore, does not require medical treatment. Others tout testosterone replacement therapy as a proverbial fountain of youth for men hoping to recapture the strength and stamina of their younger selves.

Like most controversial health issues, the truth about low T lies somewhere in the middle. While testosterone replacement therapy can make a dramatic difference in some men's lives, it's not for everyone.

"Almost every organ and tissue in a man's body has testosterone receptors," says Laurence Levine, MD, a urologist at Rush. "Testosterone plays a vital role in the proper functioning of your bones, muscles, brain, liver and everything in between."

In fact, testosterone is responsible for all of the following:

Due to the importance of testosterone in men's overall health, health care providers are increasingly recognizing low T (with varying degrees of severity) as more than just a fad. In fact, a recent study found that almost 40 percent of men over 45 years old had low testosterone.

Peaks and valleys are the norm when it comes to testosterone. Levels change several times a day; it's highest in the morning and lowest in the evening.

Throughout life, testosterone peaks in the early 30s and steadily declines with age. However, age is not the only culprit behind decreasing testosterone.

Other medical conditions that can cause low T include the following:

When low T occurs with or as the result of an existing medical condition, it can exacerbate symptoms of that condition and even accelerate disease progression.

Long-term, untreated low T can also increase the risk of age-related complications. "A man in his 50s with a long history of low T may have more rapid loss of muscle and bone. He also has a higher risk of developing dementia later in life," says Levine.

Men who have existing conditions that cause low T have been using testosterone therapy for years. Today, however, many men who do not have other medical problems are also using testosterone therapy in an attempt to feel younger, stronger and more vital.

As a result, much of the controversy surrounding low T and testosterone replacement therapy stems from determining who needs it and who doesn't.

"If you have some of the signs of low T, it does not necessarily mean your testosterone is low; and if your testosterone is low, it doesn't necessarily mean you'll have symptoms," Levine says. "To be a good candidate for treatment, you must have both low testosterone and symptoms."

Which symptoms should you watch for? According to Levine, these are the most common:

Some of these symptoms could mimic other conditions, such as depression or low thyroid function. Speak to your primary care physician or urologist to determine the cause of your symptoms, so you can make sure you get the right treatment.

Testosterone is tested with a simple blood test between 8 a.m. and 11 a.m. (when testosterone levels are highest). Normal levels fall between 300 and 1,000 ng/dL (nanograms per deciliter).

Here's what to do with your results:

"However, if I see a man who has no symptoms and his testosterone is at 150, I may recommend treatment because he could start to experience problems with cognition and frailty as he gets older," Levine says.

"The decision about whether to treat or watch and wait depends on each man's specific situation" he adds. "There's no one-size-fits-all. I always tailor the approach to the patient."

If you have low T and persistent symptoms, your doctor may recommend one of the following treatments:

"You may notice an improvement in energy and libido as quickly as a month into treatment. But typically it takes about three months of treatment to notice an obvious improvement in your symptoms," says Levine.

There are a number of concerns about the safety of testosterone replacement therapy. And most health care professionals agree more research is needed on the long-term effects of testosterone therapy.

But in the meantime, there have been some interesting findings in recent years:

However, Levine warns that testosterone can stimulate tumor growth in men who already have prostate cancer. Thus, men with existing prostate cancer will need regular monitoring with a prostate-specific antigen (PSA) test and a complete blood count every six months.

"Testosterone seems to actually have a beneficial effect on cardiovascular health," says Levine. "Studies show men with low T and heart disease who received testosterone replacement therapy had lower death rates than those who did not receive testosterone therapy."

If you have a heart condition, it is best to discuss your options with your cardiologist and men's health clinician.

"It is not a treatment for diabetes, but it can certainly help regulate glucose and metabolism," Levine says.

There are, however, some risks associated with long-term testosterone use, including the following:

Bottom line: Testosterone therapy may not be appropriate if you're just feeling a little more run down than usual. "Working closely with a trusted medical professional is the best way to determine if it is right for you," Levine says.

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The Lowdown on Low-T - Discover Health - Rush University ...