Absoludy FreeT4 is a FIA(Fluorescence immunoassay) based quantitative result diagnostic test. Thyroxine, also known as T4, is a type of thyroid hormone regulating your weight, body temperature, muscle strength, and even your mood. Measuring the level of FreeT4 to help check if three organs (hypothalamus, pituitary and thyroid) are functioning normally. Free T4 deficiency related symptoms of hypothyroidism such as weight gain, dry skin, cold intolerance, irregular menstruation, and fatigue. [AACC LAB TESTS ONLINE]