Guide to understanding Lab Results for PCOS...what if they're "normal'?
NOTE: SCROLL DOWN TO THE NEXT POST FOR A GREAT ARTICLE ON 'NORMAL' LABS and PCOS!!
Another resource for what lab tests will be ordered, how is the test done, what is the test looking for:
Comprehensive list of 'normal' ranges for various test results:
More articles on Getting a diagnosis, Learning to live with pcos, etc:
Last edited by KatCarney; 04-04-2012 at 10:50 PM.
MAKING SENSE OF YOUR LAB TESTS
Hardly a week goes by when I do not see a patient in the office who has been told that there was nothing wrong with them because their lab tests were all normal. By the time you finish this section, I hope that you will have a far better understanding as to what is really happening.
There are several reasons for the confusion. If you have seen copies of your lab tests, your result will be listed along with the normal range for that test. One of the main problems relates to the fact that the normal range that most labs list for serum androgen levels in women are wrong. I first became aware of this fact many years ago when I was seeing women with obvious androgen problems and the lab was reporting normal serum androgen levels. When I contacted the lab, they sent me a fairly complete analysis of how they derived their normal range. Usually, a lab will calculate its normal range by drawing blood from a number of individuals who are "normal" - they are free of the problem being investigated.
It became immediately apparent to me when I looked at the lab's data that they were including women with androgen problems in their normal range study. I pointed this out to them - they could care less. They did absolutely nothing to correct the error.
Another reason for the errors relates not only to the fact that the normal range as listed by most labs is wrong, the labs themselves are not terribly reliable. This was clearly shown in a study reported by Dr. Emil Steinberger, a well respected Endocrinologist who has spent his entire career looking at androgen problems in women. Dr. Steinberger drew blood from women and not only ran the tests in his own lab but sent them out to 11 commercial labs. None of the commercial labs came even close to the true value that he obtained in his lab where he was able to maintain strict control. Furthermore, virtually all of the commercial labs reported levels that were far above what they should have been.
If you look at the normal range listed by the various commercial labs for a serum testosterone in women, you will usually see a number somewhere around 70 to 75. In fact, a normal woman without an androgen problem has a testosterone level in the range of 25 to 30 - never higher.
There is another reason why the test results are incorrect and that is many physicians simply order a total serum testosterone level. If you are going to accurately assess a woman with an androgen problem, this is not the proper way to do it. To understand this, you have to understand how hormones are carried in your blood stream.
Virtually all hormones such as testosterone are attached to special serum proteins. Each hormone has its own carrier protein although some hormones will share the same protein.
This is the case for estradiol and testosterone. They both share the same carrier protein which is called "sex hormone binding globulin" - usually abbreviated "SHBG".
Virtually all of the hormone in the blood is attached to the carrier protein. Only a minute fraction is "free" or unbound. However, it is the free fraction that is biologically active. If you are going to accurately assess a woman's androgen status, it is critically important that you measure the free fraction, or at least find some way of estimating the free fraction.
The binding globulins are made in the liver. Estrogen increases the serum concentration of the various binding globulins including SHBG. Testosterone lowers the concentration of SHBG. I have seen many women who had normal serum testosterone levels but whose SHBG was quite low. This leads to an increased amount of the free or unbound testosterone since there are fewer binding sites available.
It is possible to order a free testosterone level from the lab. Another test which I frequently order is a "bioavailable" testosterone. This tells me how much of your serum testosterone is actually available to exert its actions. All of these tests are far more meaningful and informative than simply measuring the total testosterone and nothing else.
There is another simple way to estimate the free testosterone level and that is by calculating what is called the "free androgen index" or "FAI". This is a simple calculation using the SHBG as a correction factor on the total testosterone.
This sometimes gets a little confusing because it involves two different units of measurement. Until around twenty years ago or so, all values were expressed in the metric system. The total serum testosterone level is almost always expressed this way. Most labs will report the serum testosterone level in "ng/dl".
"ng" stands for nanograms. A nanogram is 10-9th grams - one billionth of a gram.
"dl" stands for deciliter - 1/10 of a liter or 100 cc's.
To try to make things uniform throughout the world, many countries have adopted the SI standard of measurement. The concentration of SHBG is usually expressed in SI units. I will not confuse you completely by trying to explain it. Nonetheless, you have to convert testosterone to the SI units in order to use the SHBG as a conversion factor.
The formula is quite simple - T X 3.47/SHBG. This means you simply take the total testosterone and multiply it by 3.47. Divide that result by the concentration of SHBG and you get a number. This number is called the free androgen index.
Because you get a pure number, it is very easy to assess a woman regardless of what other hormones she may be on, regardless of her age, regardless of whether or not she is postmenopausal, etc.
A normal woman should have an FAI less than 5. Anything over 5 is elevated.
I hope that this explanation will help to clear up any confusion you may have had. I hope it will help you understand and interpret the various lab results that you may receive.
The same explanation applies to other serum androgens that we frequently measure such as the androstenedione. Androstenedione is an important androgen in the body. 50% of the androstenedione circulating in your blood stream comes from the ovary - the other 50% comes from the adrenal gland. Again, androstenedione is bound to serum proteins though not the same ones that bind testosterone.
For most labs, the upper limit of normal for the serum androstenedione is somewhere between 250 and 270. I hope you can now appreciate that any androstenedione level that is very close to the upper limit of "normal" is almost certainly elevated. The same applies to the serum DHEAS level.
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MYTH - THERE IS A TEST FOR POLY-CYSTIC OVARY SYNDROME
More and more, I am seeing women come into the office with classic Poly-Cystic Ovary Syndrome (PCOS) who have been told that they did not have it because their blood tests were all normal. If you believe you have PCOS, it is critically important that you understand that the blood tests that I do are not to make the diagnosis (or break it), they are simply to give me baseline information to help me assess your response to future therapy.
It is critically important to understand that PCOS is a clinical diagnosis - it is based upon a woman's history and physical exam. Although there is no universally accepted definition of PCOS, most Endocrinologists would agree that two criteria must be satisfied. First, the woman must have some abnormality of ovulation and, secondly, she must have either clinical or laboratory evidence of increased androgen (male hormone) production.
The two principal physical signs of excess androgen production are either acne or hirsutism (the presence of coarse dark hair on a woman's body in locations that it should not normally be found). The vast majority of women with excess androgen production will in fact have either acne or hirsutism. There are occasional women who do not have any physical signs of excess androgen but whose blood test will clearly show it.
One of the problems that creates the confusion is the fact that, on paper, many women with obvious androgen problems have "normal" serum androgen levels. There are two reasons for this. First, although the total testosterone may be normal, the free (the biologically active portion) testosterone level is frequently elevated.
More importantly, it is important to understand that the normal range for the serum testosterone that most labs use when they report their values is seriously in error. This has been known for many many years. The labs show no inclination to change it.
Most labs report that the upper limit for a serum testosterone level in women is in the range of 60 to 75 (the numbers vary slightly from lab to lab). In fact, it has been clearly shown that when the test is done properly, a normal woman never has a testosterone level in excess of 30. Therefore, if a physician draws a testosterone level on a woman and the result comes back 50 or 60, that woman will be told that she is "normal" when in fact she is not.
This was proven quite conclusively several years ago by a well respected Endocrinologist in Texas. He drew serum testosterone levels on his patients with obvious androgen problems and sent the result to 11 different commercial labs. He got back 11 completely different results and none of the results were anywhere near the true result that he obtained when he ran the test in his own lab.
It is important that you understand this so that you realize that you may in fact have PCOS even though you have been led to believe that you do not.
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