~ The 10 Most Important Blood Tests, Part 2

7. C-Reactive Protein

Increasingly, medical science is discovering that inflammation within the body can lead to a range of life-threatening degenerative diseases such as coronary heart disease, diabetes, macular degeneration, and cognitive decline. By measuring your body’s level of inflammation through regular C-reactive protein testing, you can devise a strategy of diet, exercise, and supplementation to halt many of these conditions.

C-reactive protein (CRP) is a sensitive marker of systemic inflammation that has emerged as a powerful predictor of coronary heart disease and other diseases of the cardiovascular system.32 The highly sensitive cardiac CRP test measures C-reactive protein in the blood at very early stages of vascular disease, allowing for appropriate intervention with diet, supplements, or anti-inflammatory therapy. The cardiac CRP test detects much smaller levels of inflammation than the basic CRP test, so is therefore able to identify at-risk patients earlier, even among apparently healthy persons.

A review of epidemiological data found that high-sensitivity cardiac CRP was able to predict risk of incident myocardial infarction, stroke, peripheral arterial disease, and sudden cardiac death among healthy individuals with no history of cardiovascular disease, as well as predict recurrent events and death in patients with acute or stable coronary syndromes. This inflammatory marker provided prognostic information that was independent of other measures of risk such as cholesterol level, metabolic syndrome, and high blood pressure. Investigators concluded that greater levels of cardiac CRP are associated with higher cardiovascular risk.33


Current Laboratory Reference Range

Optimal Range

0-3 mg/L

<0.55 mg/L

0-3 mg/L

<1.5 mg/L

According to a recently published article in the journal Circulation, “In older men and women, elevated C-reactive protein was associated with increased 10-year risk of coronary heart disease, regardless of the presence or absence of cardiac risk factors. A single CRP measurement provided information beyond conventional risk assessment, especially in [men and women at intermediate levels of risk].”34

Increased levels of C-reactive protein have previously been strongly linked with a greater risk of developing type II diabetes.35 These results were confirmed in a more recent study from the Harvard School of Public Health. In a prospective study of 32,826 healthy women, elevated CRP levels were a strong independent predictor of type II diabetes. According to investigators, these data support the role of inflammation in the pathogenesis of type II diabetes.36

C-reactive protein is also an independent risk factor for the progression of age-related macular degeneration, according to recent research published in the Archives of American Ophthalmology.37 This follows a study by the same authors, in which elevated CRP levels were shown to be an independent risk factor for age-related macular degeneration, implicating “the role of inflammation in the pathogenesis of [age-related macular degeneration].”38

Elevated levels of CRP have also been associated with the loss of cognitive ability in seemingly healthy people.39 Furthermore, elevated CRP levels have been strongly associated with major depression in men.40

High-sensitivity CRP testing likewise reveals systemic inflammation that is associated with disease activity in patients with rheumatoid arthritis.41

Natural therapies may help to optimize high-sensitivity CRP levels. You may wish to discuss with your doctor the use of fish oil, L-carnitine, and soluble fiber before meals.

8. Thyroid Stimulating Hormone (TSH)

Secreted by the pituitary gland, thyroid stimulating hormone (TSH) controls thyroid hormone secretion in the thyroid. When blood levels fall below normal, this indicates hyperthyroidism (increased thyroid activity, also called thyrotoxicosis), and when values are above normal, this suggests hypothyroidism (low thyroid activity). Overt hyper- or hypothyroidism is generally easy to diagnose, but subclinical disease can be more elusive.

Because the symptoms of thyroid imbalance may be nonspecific or absent and may progress slowly, and since many doctors do not routinely screen for thyroid function, people with mild hyper- or hypothyroidism can go undiagnosed for some time. Undiagnosed mild disease can progress to clinical disease states. This is a dangerous scenario, since people with hypothyroidism and elevated serum cholesterol and LDL have an increased risk of atherosclerosis.

Mild hypothyroidism (low thyroid gland function) may be associated with reversible hypercholesterolemia (high blood cholesterol) and cognitive dysfunction, as well as such nonspecific symptoms as fatigue, depression, cold intolerance, dry skin, constipation, and weight gain. Mild hyperthyroidism is often associated with atrial fibrillation (a disturbance of heart rhythm), reduced bone mineral density, and nonspecific symptoms such as fatigue, weight loss, heat intolerance, nervousness, insomnia, muscle weakness, shortness of breath, and heart palpitations.

One study found that TSH levels greater than 2.0 mU/L increase the 20-year risk of developing hypothyroidism,42 while another study found that TSH levels greater than 4.0 mU/L increase the risk of heart attack in elderly women.43 Recently, published data showed that sub-clinical hypothyroidism was associated with an increased risk of congestive heart failure among older adults with TSH levels of 7.0 mU/L or greater.44


Current Laboratory Reference Range

Optimal Range

0.35-5.50 mU/L

0.35-2.1 mU/L

In healthy postmenopausal women, TSH levels at the low end of the normal range (0.5-1.1 mU/L) are associated with low bone mineral density and a 2.2-fold greater risk of osteoporosis, according to a study published in 2006 in the journal Clinical Endocrinology.45

Measuring TSH is the best test for assessing thyroid function. Currently, the American Thyroid Association recommends screening for TSH levels beginning at age 35, and every five years thereafter.46 If results are abnormal, assessing TSH in conjunction with levels of tri-iodothyronine (T3) and thyroxine (T4) blood levels may help assist definitive diagnosis.

Natural therapies may help to support thyroid health and optimize TSH levels. You may wish to discuss with your doctor the use of L-tyrosine, iodine, and selenium.

9. Testosterone (Free)

Testosterone is produced in the testes in men, in the ovaries in women, and in the adrenal glands of both men and women. Men and women alike can be dramatically affected by the decline in testosterone levels that occurs with aging.

In the serum of both men and women, less than 2% of testosterone typically is found in the free (uncomplexed) state. Unlike bound testosterone, the free form of the hormone can circulate in the brain and affect nerve cells. Testosterone plays different roles in men and women, including the regulation of fertility, libido, and muscle mass. In men, free testosterone levels may be used to evaluate whether sufficient bioactive testosterone is available to protect against abdominal obesity, mental depression, osteoporosis, and heart disease. In women, low levels of testosterone have been associated with decreased libido and well-being, while high levels of free testosterone may indicate hirsuitism (a condition of excessive hair growth on the face and chest) or polycystic ovarian syndrome. Increased testosterone in women may also indicate low estrogen levels.

Men: In men, testosterone levels normally decline with age, dropping to approximately 65% of young adult levels by age 75.47 This drop in testosterone is partially responsible for the significant physiological changes seen in aging men. In fact, low levels of testosterone are associated with numerous adverse health conditions, including diminished libido, metabolic syndrome,48 erectile dysfunction, loss of muscle tone, increased abdominal fat, low bone density, depression,49 Alzheimer’s disease,50 type II diabetes,51 and atherosclerosis.52


Standard Reference Range

Optimal Range

6.6-26.5 pg/mL

15-26.5 pg/mL


Standard Reference Range

Optimal Range

0-2.2 pg/mL

1.4-2.2 pg/mL

New research shows that low testosterone levels are a risk factor for ischemic heart disease in men. Recent research published in the journal Endocrinology Research showed a relationship between decreased testosterone levels and increased severity of thoracic aortic atherosclerosis in men.53

Women: Following menopause, levels of testosterone in women decrease, along with a concomitant decline in libido, mood, and general well-being. Although women produce only small quantities of testosterone, evidence indicates that this important hormone helps women maintain sexual function, as well as muscle strength and mass. Investigators reporting in the Journal of Clinical Endocrinology and Metabolism found that when obese women were given low doses of a synthetic testosterone analogue, they lost more body fat and subcutaneous abdominal fat, and gained more muscle mass, than women given placebo. The testosterone-supplemented women also experienced a slight increase in resting metabolic rate.54

Optimal testosterone levels may support healthy mood, libido, body composition, and cardiovascular wellness. You may wish to discuss with your doctor the use of supplements such as DHEA and pregnenolone. Speak to your physician to determine whether prescription testosterone may also be helpful for you.

10. Estradiol

Like testosterone, both men and women need estrogen for numerous physiological functions. Estradiol is the primary circulating form of estrogen in men and women, and is an indicator of hypothalamic and pituitary function. Men produce estradiol in much smaller amounts than do women; most estradiol is produced from testosterone and adrenal steroid hormones, and a fraction is produced directly by the testes. In women, estradiol is produced in the ovaries, adrenal glands, and peripheral tissues. Levels of estradiol vary throughout the menstrual cycle, and drop to low but constant levels after menopause.

In women, blood estradiol levels help to evaluate menopausal status and sexual maturity. Increased levels in women may indicate an increased risk for breast or endometrial cancer. Estradiol plays a role in supporting healthy bone density in men and women. Low levels are associated with an increased risk of osteoporosis and bone fracture in men and women as well. Elevated levels of estradiol in men may accompany gynecomastia (breast enlargement), diminished sex drive, and difficulty with urination.

Women: Diminished levels of estradiol correlate with low levels of bone mineral density, which is a strong risk factor for osteoporosis.55 Optimizing estradiol levels in early menopausal women has been associated with relief from hot flashes, irritability, and insomnia.56

According to a recently published report from the University of Michigan School of Public Health, lower estradiol levels in women are associated with higher levels of markers of cardiovascular disease risk.57

Men: In older men, low levels of estradiol have been linked with an increased risk of vertebral fractures;58 conversely, estradiol levels are found to be positively associated with bone mineral density, suggesting an association between low serum levels and the development of osteoporosis.59 A recent study from France found a correlation between low estradiol and skeletal frailty.60


Standard Reference Range

Optimal Range

<54 pg/mL

10-30 pg/mL


Standard Reference Range

Optimal Range

0-528 pg/mL

352-528 pg/mL

Significant positive correlations were found between estradiol levels and levels of total cholesterol, according to results from a recently published study of 111 men with stable coronary artery disease. Researchers suggested that estradiol has a possible role in “promoting the development of atherogenic lipid milieu in men with coronary artery disease.”61

Optimal estradiol levels may support healthy bone density, cardiovascular health, and well-being. You may wish to discuss with your doctor the use of supplements such as DHEA, pregnenolone, soy, black cohosh, and pomegranate. Speak to your physician to determine whether prescription therapies such as bioidentical estrogens may also be helpful for you.


Yearly blood testing is a simple yet powerful strategy to help you proactively take charge of your current and future health. A well-chosen complement of blood tests can thoroughly assess your overall state of health, as well as detect the silent warning signals that precede the development of serious diseases such as diabetes and heart disease.

Many diseases and disorders are treatable when caught early, but can severely impair the quality and length of your life if left unattended. Identifying these hidden risk factors will enable you to implement powerful strategies such as proper nutrition, weight loss, exercise, supplements, and medications in order to prevent progression to full-blown, life-threatening diseases. Blood testing can also detect biochemical changes that threaten well-being and quality of life, such as declining levels of sex hormones.

Armed with information on important health biomarkers, you and your physician can plan and execute a strategy to help you achieve and maintain vibrant health.

Ordering blood tests can be easy and convenient. Just call 1-800-208-3444 to be directed to a blood testing laboratory in your area.

References . . .

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