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Life Extension Magazine May 2011
Report

Do You Know Your Sex Hormone Status?

By Zach White
Protection from Cancer

Protection from Cancer

Many kinds of cancers of the breast and prostate are stimulated by the sex hormones estrogen and testosterone. However, SHBG interpretations differ for men and women, which is why the SHBG test requires professional interpretation for accurate application.

For example, in human breast cancer cells, higher levels of SHBG inhibit cell proliferation and promote programmed cancer cell death (apoptosis), by blocking the estrogen-related survival mechanisms that most breast cancer cells exploit.43-46

For men, it is the opposite. Higher SHBG levels predict more severe and invasive tumor growth in men with prostate cancer.47 The association is so strong that some urologists have suggested using SHBG levels as a standard pre-operative measurement to identify patients at high risk of invasive cancers who should undergo a more aggressive surgical procedure.48

Optimizing Bone Health

It has long been known that declining estrogen levels in both sexes are significant contributors to bone mineral loss with aging. Experts now recognize that the steady rise in SHBG with aging is directly correlated with bone loss and osteoporosis in both men and women.49-56 As a general rule the higher the SHBG level, the less estrogen is available to contribute favorably to bone health.

New studies, however, are finding a direct role for SHBG and its cell surface receptor in bone loss.57 That suggests an effect that may be independent of estrogen levels. The association is so strong that some experts are now suggesting routine measurement of SHBG as a useful new marker for predicting severity of osteoporosis.57

Understanding Sex Hormone Levels

The terminology for the different measurements of sex hormones in your blood can be confusing, but it needn’t be. Here’s a simple way to think about the levels, using testosterone as an example:16

Total Testosterone (T) is just that—a measurement of all of the testosterone in a given blood sample. It includes free T, T bound to SHBG, and T bound to albumin.

Free Testosterone is equally simple in concept, though harder to measure. Free T is that small proportion (0.5-3%) of testosterone not bound to SHBG or to albumin.17

Bioavailable Testosterone (bioT) is simply the combination of the small amount of free T, plus the much larger amount of T that is loosely bound to albumin. You can also think about bioT as the amount of T that is not bound to SHBG, and some scientists refer to it that way.22,24,61 In general, higher SHBG will mean there’s less T that is bioavailable, while lower SHBG means there’s more bioavailable T, though that is a bit of an oversimplification.

The test for SHBG is useful for understanding and optimizing your sex hormone levels in combination with your other test results. When you receive your blood test results back, if you have any questions about your sex hormone status (including SHBG levels), please reach out to a Life Extension Health Advisor at 1-866-864-3027.

Detecting Obstructive Sleep Apnea

Sex hormone-binding globulin may provide an important clue that an individual is affected by obstructive sleep apnea,7,58 a relatively common condition that increases the risk of heart disease and stroke.59

Obstructive sleep apnea occurs when breathing repeatedly stops and starts during sleep due to blockage of the upper air passages. Frighteningly, many people are unaware that they suffer from this disorder. Sleep apnea often manifests with loud snoring, waking up feeling unrested, morning headaches, daytime sleepiness, fatigue, and unexplained high blood pressure. An overnight sleep study (polysomnography) is essential in order to definitively diagnose the condition.60

Scientists have found that obstructive sleep apnea is associated with disruptions in the endocrine system in men, including decreased levels of SHBG as well as free and total testosterone.7,58 Lower levels of SHBG, free testosterone, and total testosterone correlate with more severe sleep apnea.7,58 In one study, men’s SHBG and total testosterone rose significantly following 3 months of sleep apnea treatment with continuous positive airway pressure (CPAP).7

Detecting Obstructive Sleep Apnea

Low SHBG combined with low testosterone may represent a novel marker for sleep apnea in men and may provide helpful information regarding which individuals should consider having a sleep study to diagnose the condition.

Summary

Maintaining optimal sex hormone status, including a healthy balance of testosterone and estrogen, is a core component of any anti-aging strategy. New scientific evidence has revealed the crucial importance to hormone balance of a widely overlooked active protein called sex hormone-binding globulin or SHBG. It is an important regulator of your testosterone and estrogen levels, responsible for distributing sex hormones throughout your body—yet few doctors test for it.

SHBG abnormalities are associated with multiple killer diseases of aging in both sexes, including cardiovascular disease (especially in women), cancer, type 2 diabetes, metabolic syndrome, sleep apnea, and osteoporosis.

If you have any questions on the scientific content of this article, please call a Life Extension® Health Advisor at
1-866-864-3027.

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