Total T4 (Thyroxine) Test

Our Total T4 Test measures the total levels of T4 (also known as thyroxine) in the blood. The T4 test is used to assess how the thyroid is functioning and to help detect imbalances with the thyroid, like hyperthyroidism and hypothyroidism. T4 is a hormone that plays a role in growth and metabolism. It is produced by Thyroid Stimulating Hormone (TSH).

There are two kinds of T4 tests: Total T4 and Free T4 (FT4); this is the Total T4 test, meaning it measures both Free T4 (thyroxine that has not bonded to proteins in the blood) and T4 that is bonded to proteins in the blood (most T4 is bonded).

The Total T4 Test can help diagnose the follow thyroid issues:

• Hypothyroidism (underactive thyroid)
• Hyperthyroidism (overactive thyroid)
• Hypopituitarism (occurs when the pituitary gland is underactive)
• Thyrotoxic Periodic Paralysis