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Hormonal Bioavailability

Meaning

Hormonal bioavailability quantifies the fraction of a hormone that is actively available to interact with its specific receptors in target tissues and subsequently elicit a biological effect. This measure is critically important because only the unbound, or free, portion of a hormone is generally considered biologically active, as the protein-bound fraction is inert for immediate cellular signaling. Clinical assessment of this parameter is vital for accurately diagnosing states of hormone excess or deficiency, particularly when total hormone levels alone might be misleading due to binding protein fluctuations.