This protein is produced primarily in the liver, although testes, uterus, brain and placenta also synthesize it. It serves as the transport carrier, shuttling testosterone and estrogen throughout the body. It also safeguards these hormones from degrading too rapidly and prevents clearance from the body.
Sex Hormone Binding Globulin (SHBG) also conveys essential signals to the heart, brain, and adipose tissue to ensure optimal function. Cell surfaces have a special SHBG receptor molecule like vitamin D receptor protein, which helps cells communicate with each other so it functions like a hormone.
As one ages SHBG rises, even as sex hormone levels decline so bioavailability of sex hormones declines. Therefore, overall levels of a hormone, such as testosterone, may be normal but person may be testosterone deficient as most of the hormone is bound to albumin or SHBG. This may lead to feminization of men, as circulating estrogen's physiological influence is left unchecked due to the lack of free testosterone. This leads to gynecomastia (enlarged breasts in men), decreased libido, poor sexual performance, cognitive decline and chronic fatigue.
Low total testosterone and low SHBG are predictors for high incidence of metabolic syndrome and its complications. In late postmenopausal women, low SHBG and high estrogen correlate with the inflammatory state associated with metabolic syndrome. SHBG abnormalities have also been linked to acne, infertility, polycystic ovary syndrome and uterine cancer. High insulin levels also "suppress" SHBG.
Causes of Condition
- Cardiovascular Disease - Low SHBG is associated with elevated levels of C-reactive protein. Low levels are also strongly correlated with obesity.
- Low SHBG is associated with arterial calcification, elevated triglycerides and elevated low-density lipoprotein (LDL).
- Cancer - High levels of SHBG suppress human breast cancer cell proliferation and promote programmed cancer cell death (apoptosis).
- Bones - Rising SHBG levels is directly related to bone loss and osteoporosis in both men and women. The higher the SHBG, the lower the level of available estrogen available to contribute to bone health. There is also a direct role for SHBG and its cell surface receptor in bone loss.
- Sleep Apnea - Obstructive sleep apnea is associated with decreased levels of SHBG, free testosterone and total testosterone in men.
- Total testosterone - Free testosterone plus testosterone bound to albumin and SHBG.
- Free testosterone - Only 0.5-3.0% of Testosterone is not bound.
- Bio-available Testosterone - Combination of free testosterone plus total testosterone loosely bound to albumin therefore higher SHBG, the less bio-available testosterone.
Bio-identical Hormone Replacement Therapy could possible prevent or reverse these affects. Additionally, specific vitamins, minerals, and diet can aid in this as well.Overall, this issue is very complicated therefore Dr. Allibone manages each patient on an extremely individualized basis. Blood tests, medical history, diet, etc. will all be looked at to find the exact root of the problem instead of simply managing the symptoms. By using this specialized approach, each patient can be put on the path to optimal health. Back to Top
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If we fill our hours with regrets of yesterday and with worries of tomorrow, we have no today in which to enjoy our existence. Seize the day, and take control of your health and life. How you are going to live those tomorrows will depend on how you act and choose today. - George Allibone M.D.