What is the Origin of Free Hormone Assays?

This term is specific to clinical endocrinology, differentiating between total hormone measurements and the metabolically relevant "free" fraction. The "Assay" component refers to the analytical method used for quantification.

What is the Mechanism of Free Hormone Assays?

The assay mechanism typically employs equilibrium dialysis or sensitive immunoassays designed to selectively quantify the small percentage of hormone not attached to Sex Hormone Binding Globulin or Thyroid Binding Globulin. This measurement directly correlates with the hormone's effective biological activity at the cellular receptor level.

Free Hormone Assays

Meaning

Laboratory tests designed to accurately measure the concentration of biologically active, unbound hormones circulating in the blood, such as free testosterone or free T4, rather than the total amount bound to carrier proteins. These assays provide a more accurate reflection of the hormone available to interact with target tissues. Clinical interpretation relies heavily on these unbound fractions.