Posted 7/8/2019 8:02 AM (GMT -7)
All you ever wanted to know about T testing. Have your blood draw before 10AM, which Tall Allen suggested, and I was trying to verify. As usual, he's correct.
Diagnosing and confirming low testosterone requires thorough lab testing and careful interpretation of the results.
Feeling less pep in your step? Less interested in sex? Befuddled by a persistent brain fog that hobbles your mood and mental performance? There are many reasons why you might feel this way. Testosterone deficiency is but one possibility.
The number of men diagnosed with "low T" has grown dramatically in recent years. Your doctor may consider a trial run of testosterone injections or a rub-on gel if you report classic signs of testosterone deficiency and if lab tests confirm that your hormone levels are abnormally low. But testing testosterone is tricky.
"The first step is finding out if you have low testosterone to start, which is complicated by the fact that we have no really reliable way to measure it," says Dr. William Kormos, editor in chief of Harvard Men's Health Watchand a primary care physician at Massachusetts General Hospital.
Inaccurate or misinterpreted test results can either falsely diagnose or miss a case of testosterone deficiency. And because the treatment is not without risks, it's important to have your testosterone levels assessed carefully before considering supplementation.
What does 'total testosterone' measure?
What does ‘total testosterone’ measure?
A "total" testosterone lab test measures free testosterone as well as the amount of hormone bound to the proteins albumin and sex hormone binding globulin (SHBG). Free and albumin-bound hormone are "bioavailable" and thus active in the body.
First step: Identify symptoms
The first step in diagnosing testosterone deficiency is establishing whether a man has the classic symptoms. Guidelines released in 2010 by the Endocrine Society cited a list of "red flags" that raise the possibility of low T. These are low libido, erectile dysfunction, low sperm count, loss of body hair, and hot flashes. Other signs that could prompt your doctor to suspect low testosterone are poor concentration and memory; feeling sad or blue; insomnia; decreased energy, motivation, initiative, or self-confidence; decreased muscle mass and increased fat; and diminished physical or work performance.
Which symptoms are the most important? It's a judgment call. "Very few people have every single one of them," says Dr. Abraham Morgentaler, an associate clinical professor of urology at Harvard-affiliated Beth Israel Deaconess Medical Center, and author of the book Testosterone for Life. "The more symptoms he has the more likely he is deficient."
But what man hasn't felt irritable and pooped out, or had a less-than-satisfying sexual encounter? If diagnosing testosterone deficiency were based solely on a list of such general symptoms, virtually every man would be labeled as low T.
"The problem is that the symptoms of testosterone deficiency are really common, and they are also common in men who have normal testosterone," says Dr. Carl Pallais, an endocrinologist and assistant professor of medicine at Massachusetts General Hospital.
Measuring total testosterone
If the classic symptoms of low testosterone are present, the next step is to measure the level of testosterone in the blood. But determining if a man is truly deficient in testosterone is far from simple. "The test for total testosterone is not a terrifically reliable test," Dr. Morgentaler says.
For one thing, total testosterone fluctuates quite a bit during the day. Testosterone levels are highest in the morning, although this effect is less pronounced in older men. To get the best result, physicians generally draw blood for testosterone lab tests between 7 a.m. and 10 a.m.
After measuring your testosterone, your doctor must determine if it is in the normal range. Across the total population of men, the statistical norm for testosterone ranges from about 270 to 1070 nanograms per deciliter (ng/dL). So if your total testosterone is below 270, that must mean you are deficient, right?
Unfortunately, the definition of "low" depends on the local standard adopted by the doctor and the testing lab. The line at which you cross into "low T" can be 230, 250, 270, or 300. "There is no agreement in the labs on this, which adds to the confusion," Dr. Morgentaler says.
Also, the measured testosterone levels vary from test to test and from lab to lab. "For people with borderline-low testosterone levels, if you repeat the test about 30% of them will then be in the normal range," Dr. Pallais says.
Three kinds of testosterone
The main issue with the total testosterone lab test is that a lot of the hormone it measures is not biologically active in the body. "Total testosterone is not what the body really cares about," Dr. Pallais explains. "This can make it hard to interpret test results that are low-normal."
Here is why: A small fraction of the total testosterone, from 1% to 2%, floats around on its own in the blood. This "free" testosterone is biologically active. about half the remaining hormone is loosely attached to a protein called albumin. This kind of testosterone, like free testosterone, is potentially available for work. The two, together, represent the "bioavailable" hormone the body's tissues actually respond to.
But anywhere from 40% to 70% of total testosterone travels around with a protein called sex hormone binding globulin (SHBG). It is bound so tightly to SHBG that it can't be released, and therefore isn't available to your cells.
As a result, a large portion of your measured total testosterone actually may be biologically inactive. This can be misleading in certain circumstances. "If the levels are borderline low, that's where the real problem is," Dr. Pallais says. "You don't know if it's real or if it's a variation in SHBG levels."
For example, if a man's SHBG is on the high side, his total testosterone may be solidly in the normal range even though his biologically active testosterone is low. The opposite is true, too: If the SHBG is low, a man's total testosterone level may look abnormally low even though his bioavailable testosterone level is well within the norm.
"SHBG is the joker in the deck," says Dr. Morgentaler, director of Men's Health Boston, which treats many men with low testosterone. "High levels in a man can make his total testosterone appear perfectly normal even though he has every symptom in the book, and his tissues are truly deficient in testosterone."
Why not, then, just test free testosterone and avoid the whole SHBG issue? Unfortunately, lab tests for free testosterone are also unreliable—even more so than tests for total testosterone. "If you run the same person's blood on the same test three times, you get different answers," Dr. Kormos says. In fact, a study by the Endocrine Society found that measurements of free testosterone in the same blood sample can vary by a factor of five.
How to get a good diagnosis
To obtain a clear-cut diagnosis —either confirming low T or ruling it out—work with a physician who understands the complexities of testosterone testing and can interpret the results in light of a man's symptoms, says Dr. Cigdem Tanrikut, director of male reproductive medicine at Massachusetts General Hospital. "There is not one totally foolproof test or procedure," Dr. Tanrikut says. "The physician should really look at the big picture."
A careful evaluation could involve testosterone measurements on more than one day, as well as tests for levels of hormones related to testosterone. And don't be afraid to ask for a second opinion, Dr. Tanrikut says. "I would encourage men to not be shy about seeking the opinion of a specialist who deals with testosterone issues on a regular basis."
Even when lab tests don't show clear testosterone deficiency, the final decision to offer treatment is a judgment call. "If a man has symptoms consistent with testosterone deficiency and a low-normal testosterone level," Dr. Tanrikut says, "I will still consider discussing with him the risks and benefits of a trial of testosterone replacement to see if this may help alleviate some of his symptoms."
Possible symptoms of low testosterone
According to the Endocrine Society, red flags for testosterone deficiency could include:
low sperm count
loss of body hair
The Endocrine Society also suggests that doctors consider checking testosterone if a man is experiencing certain other signs, such as:
poor concentration and memory
feeling sad or blue
decreased energy, motivation,
initiative, or self-confidence
diminished physical or work performance
reduced muscle bulk and strength; increased body fat
Is it safe?
Some men may experience certain side effects of testosterone supplementation, including acne, swelling or tenderness of the breasts, or swelling in the ankles. Doctors also watch for high red blood cell counts, which could mean an increased risk of clotting.
Some physicians remain wary of prescribing testosterone supplements to men with active prostate cancer, those who had it in the past, or those who may be at higher risk for it in the future. The reason: In men with advanced prostate cancer, blocking testosterone slows down tumor growth. The concern is whether boosting hormone levels could activate early cancer or speed up tumor growth in men who already have prostate cancer.
The topic is hotly debated. Dr. Morgentaler and other experts insist there is no evidence of such a risk. But Dr. Pallais says we don't yet have high-quality evidence from a large clinical trial to settle the question either way. Until then, he and some other physicians continue to practice as if testosterone and prostate cancer don't mix. "What is the danger?" he says. "We don't know."
By undergoing thorough testing, you can find out if you should even be considering treatment for low testosterone. And if you do try it, remember it's just a trial run. "If a man does not have an adequate subjective clinical improvement in three to six months," Dr. Tanrikut says, "we can stop the treatment."