Free thyroxine (Free T4) (Free Thyroxine, FT4, Serum)
The test determines the level of free thyroxine (T4) — the primary thyroid hormone. Free T4 reflects true thyroid hormonal activity and is independent of transport protein levels. Used to diagnose hypo- and hyperthyroidism and to monitor thyroid disease treatment. Recommended for fatigue, drowsiness, weight gain or loss, edema, thermoregulation disorders.
What the test evaluates:
- Free thyroxine level in blood serum
- Thyroid gland functional state
Biomaterial: Venous blood (serum)
- Draw blood fasting
- Exclude intense physical activity 24 hours before
Medications:
- If possible, do not take thyroid hormones 24-48 hours before (consult physician)
- Iodine preparations and biotin may affect results
- Inform physician of all medications taken
Recommended for:
- Suspected thyroid gland diseases
- Hormonal disorder symptoms
- Infertility and menstrual cycle disorders
- Heart rhythm disorders
Elevated free T4: may indicate hyperthyroidism or thyrotoxicosis
Reduced free T4: may indicate hypothyroidism
Note: Combination with TSH and free T3 required; endocrinologist consultation mandatory.