T4 Detail

The Total Thyroxine (T4) test measures the combined amount of free and protein-bound thyroxine in the blood. T4 is one of the main hormones produced by the thyroid gland, and it plays a critical role in regulating the body’s metabolism, energy production, temperature control, and growth.

This test helps in diagnosing and monitoring:

• Hypothyroidism (low T4 levels)

• Hyperthyroidism (high T4 levels)

• Thyroid hormone therapy response

Since most of the T4 in the bloodstream is bound to proteins and inactive, Total T4 gives an overall picture, but may be influenced by changes in protein levels, pregnancy, medications, or liver disease. Therefore, it is often used along with TSH and sometimes Free T4 for a more accurate evaluation.