|A Comprehensive Guide to Preventative Blood Testing|
By Penny Baron
Another example of flawed reference ranges can be seen in a blood test used to assess thyroid status known as the thyroid stimulating hormone (TSH) test. The TSH reference range used by many laboratories is 0.2-5.5 mU/L. A greater TSH level is indicative of a thyroid hormone deficiency. That is because the pituitary gland is over-signaling TSH due to low levels of thyroid hormone in the blood. Any reading over 5.5 alerts a doctor to a thyroid gland problem and that thyroid hormone therapy may be warranted.
The trouble is that the TSH reference range is so broad that most doctors will interpret a TSH reading as low as 0.2 to be as normal as a 5.5 reading. The difference between 0.2 and 5.5, however, is 27-fold, a parameter far too great to indicate optimal or even normal thyroid function.
A review of published findings about TSH levels reveals that readings over 2.0 may be indicative of adverse health problems relating to insufficient thyroid hormone output. One study showed that individuals with TSH values over 2.0 have an increased risk of developing overt hypothyroid disease over the next 20 years.16 Other studies show that TSH values over 1.9 indicate abnormal pathologies of the thyroid, specifically autoimmune attacks on the thyroid gland itself that can result in significant impairment.17
A more startling study showed that TSH values over 4.0 increase the prevalence of heart disease, after correcting other known risk factors.17 Another study showed that administration of thyroid hormone lowered cholesterol in patients with TSH ranges of 2.0-4.0 but had no effect in lowering cholesterol in patients whose TSH range was 0.2-1.9.18 It also showed that in people with elevated cholesterol, TSH values over 1.9 could indicate that a thyroid deficiency is the culprit, causing excess production of cholesterol, whereas TSH levels below 2.0 would indicate a normal thyroid hormone status.
Doctors routinely prescribe cholesterol-lowering drugs to patients without properly evaluating their thyroid status. Based on the evidence presented to date, it might make sense for doctors to first attempt to correct a thyroid deficiency (based on a TSH value over 1.9) instead of resorting to cholesterol-lowering drugs.
In a study done to evaluate psychological well-being, impairment was found in patients with thyroid abnormalities who were nonetheless within “normal” TSH reference ranges.19 The authors of a study published in the August 3, 2002 issue of The Lancet stated that “the emerging epidemiological data begin to suggest that TSH concentrations above 2.0 (mU/L) may be associated with adverse effects.”
When it comes to assessing hormone status, the use of standard reference ranges has failed aging people because reference ranges are adjusted to reflect a person’s age. Since it is normal for an aging person to have imbalances of critical hormones, standard laboratory reference ranges are not flagging dangerously high levels of estrogen and insulin or deficient levels of testosterone, thyroid, and DHEA. The table above shows standard hormone blood reference ranges for men (age 60) and compares them to what the “optimal” ranges should be.
Defying the Reference Ranges
Traditional medical thinking accepts that imbalances of life-sustaining hormones are “normal” in aging people. Traditional practitioners almost never test hormone levels because they think that nothing should be done to restore hormone profiles to youthful ranges. More and more, however, aging people are seeking the health and vitality of a younger person. If you are 80 years old and are told that your hormone profile is normal for your age, tell your doctor that you would prefer the hormone profile of a 25-year-old because you perceive a 25-year-old as having more vitality and a reduced risk of contracting lethal diseases.
The Most Important Blood Tests
The Life Extension Foundation suggests that a basic battery of tests be performed annually. The recommended “Male Panel” consists of a complete blood count (CBC)/chemistry test, homocysteine, total and free testosterone, estradiol, prostate-specific antigen (PSA), and DHEA. The recommended “Female Panel” consists of the complete CBC/chemistry test, estradiol, progesterone, total and free testosterone, DHEA, and homocysteine.
If a serious abnormality is detected—such as elevated homocysteine, hormone imbalance, high PSA—testing should be repeated more often to determine the benefits of whatever therapy you are using to correct the potentially life-shortening abnormality.
We also recommend that you consult with your physician regarding any other test that may be appropriate for your individual condition. The remainder of this article provides detailed information about individual tests and ranges that can be used to assess your health and longevity. At the end of this article, we provide information about the new lower cost blood testing available to Life Extension members.
Male and Female Testing Panels
These panels are comprised of the most requested tests, which also happen to be the best and most comprehensive screening tests capable of identifying many common and not so common conditions, identifying risk factors for future disease, and offering a clinical snapshot of your current physiologic well-being.
Both panels consist of a full chemistry and complete blood count (CBC) measuring 35 different blood components, which assess cholesterol and triglyceride levels, blood glucose, iron and mineral levels, kidney and liver function, and blood cell components.
The male and female panels also test for levels of total and free testosterone, DHEA-S (an indicator of adrenal cortical function), estradiol, homocysteine, and C-reactive protein. Both homocysteine and C-reactive protein, along with levels of cholesterol lipoproteins, are powerful predictors of cardiovascular disease.
The male panel also includes the PSA (prostate specific antigen) test, which is a very sensitive marker for prostate cancer. The female panel includes a test for progesterone levels, providing information concerning female fertility, ovulation cycles, and possible hormonal tumors.
Following are snapshots of the various tests offered in the male and female test panels.