Free T4 / Thyroxine (T4) Free
336

Information

Free thyroxine (Free T4) is used to evaluate thyroid function independent of binding protein status. The test measures serum thyroxine (T4) that is not bound to thyroid hormone-binding proteins (thyroid hormone-binding globulin [TBG], transthyretin, albumin) and is thus readily available to target cells. This test is used with thyroid-stimulating hormone measurement in the diagnosis of hyperthyroidism and hypothyroidism (low FT4), including congenital and acquired hypothyroidism.

Synonyms: FT4

Methodology
ICMA
Specimen Required

SST, Serum. Volume 1 (0.5) mL serum. Stability: Refrigerated – 4 Days, Frozen – 2 Months

CPT Code(s)
84439