# Free Testosterone **Free testosterone** refers to the portion of testosterone in the bloodstream that is not bound to carrier proteins, such as sex hormone-binding globulin (SHBG), and is therefore available for use. In contrast, total testosterone encompasses both free and bound testosterone, providing a comprehensive measure of the hormone's presence in the blood. The distinction between these two forms is crucial because only free testosterone is bioavailable and can exert its effects on the body. This includes aiding in muscle development, enhancing strength, and boosting the body's oxygen-utilizing capacity during exercise. For men, maintaining adequate levels of free testosterone is essential for bone health and preventing age-related bone loss. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.beoptimal.ca/biomarker-panels/male-performance-panel/free-testosterone.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.