Skip to main content

Free Hormones

Meaning

Free hormones represent the fraction of a specific circulating hormone that is unbound to plasma proteins, such as sex hormone-binding globulin or albumin. This unbound state is physiologically crucial because only free hormones are biologically active and capable of diffusing across cell membranes to interact with their cognate intracellular receptors. The concentration of these hormones, not the total concentration, accurately reflects the magnitude of hormonal signaling at the tissue level. Clinically, measuring free hormone levels provides a precise metric for assessing true endocrine status.