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How are testosterone levels measured?

Dr. Michael Roizen, MD
Internal Medicine
While the majority of erectile-dysfunction cases are caused by vascular issues, about 20 percent are associated with low testosterone levels. As part of a checkup to determine the root of erectile difficulties, your doctor could measure your hormone levels. Though it's a simple blood test, it's unlike most others, because testosterone is not measured directly.

To get an accurate assessment of your testosterone levels, you need to have two measurements. One measures the combined level of bound testosterone and free testosterone (the active kind that matters in terms of what symptoms you're experiencing) in your blood, while the other measures only the testosterone that's bound to proteins. By subtracting the second number from the first, you'll find your level of free testosterone. Because free testosterone can bind protein in a test tube, and bound testosterone can be displaced, the resulting number will be, at best, a close approximation.
You: Staying Young: The Owner's Manual for Extending Your Warranty

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You: Staying Young: The Owner's Manual for Extending Your Warranty

International bestselling authors of YOU: The Owner's Manual and YOU: On a Diet give you all the tools and know-how to stay young and defy the ageing process. Drawing lively parallels between your...

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