Ft4

Acroynm for free thyroxine (T4). Thyroid hormones are only biologically available and effective in free form. The majority of thyroid hormones are protein-bound. The advantage of the determination of free hormones is the independence of the binding capacity and concentration of the transport proteins (e.g. thyroxine-binding globulin).

test material: serum, plasma

Determination method: highly sensitive immunoassays

Reference values for fT4:

• children (prepubertal): 10.3-28.3 pmol/l
• Children (adolescent): 10,3-29,6 pmol/l
• Adults: 10-23 pmol/l

Elevated values: manifest hyperthyroidism

Decreased values: manifest hypothyroidism

1. Böhm BO (2018) Thyroid hormones. In: Neumeister B et al. (Eds) Clinical guide to laboratory diagnostics.