The Free Thyroxine (Free T4) test measures the level of a hormone called free thyroxine (free T4) in your blood. T4 is produced by your thyroid gland and helps control your metabolism. This test is used to help diagnose thyroid disorders such as hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid). It can also be used to monitor the effectiveness of treatment for thyroid disorders.

Free T4 (Free Thyroxine) is the biologically active form of thyroid hormone that directly enters and affects body tissues.

Key Characteristics: • Represents approximately 0.05% of circulating T4 • Metabolically active hormone • Travels freely into body tissues

Normal Range: • 0.8 to 1.9 nanograms per deciliter (ng/dL) • 10.3 to 24.5 picomoles per liter (pmol/L) • Alternative range: 0.8 to 2.0 ng/dL

Clinical Significance: • Indicates thyroid gland function • Helps diagnose: • Hyperthyroidism (elevated levels) • Hypothyroidism (low levels)

Important Considerations: • More accurate diagnostic marker than Total T4 • Preferred by medical experts for thyroid assessment •

Levels can be affected by: • Protein binding variations • Pregnancy • Medications

The Free T4 test provides healthcare providers with a precise assessment of thyroid hormone activity and potential metabolic dysfunction.