Most of the free hormone immunoassays in current use employ a specific, high affinity hormone antibody to sequester a small amount of total hormone from the specimen. The unoccupied antibody ...

namely thyroid-stimulating hormone (TSH), free thyroxine (T4), and free triiodothyronine (T3). These tests give vital insights into thyroid function and can detect issues before symptoms appear.

Traditionally, the free thyroxine index, sometimes called a "T7" is derived from the product of a T3-uptake test and a TT4 measurement, often expressed as a % uptake (adsorbent bound counts ...