T4 Total


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Quest Diagnostics Test Code: 867

T4 (Thyroxine), Total test is done for diagnosis of hypothyroidism and hyperthyroidism.

T4, also known as thyroxine, is a hormone that is released from the thyroid gland. Together with the hormone T3, they help to regulate body metabolism and energy expenditure rate. T4 is released into the bloodstream from the thyroid gland and travels to its target organs while being bound to plasma proteins. When T4 is bound to plasma proteins, it is in its inactive form. The total measurement of T4 in the blood is measured by the amount of free T4 plus bound T4. This test is performed as a marker of thyroid function, for disease like hyper and hypothyroidism, and is commonly used in conjunction with a TSH test.

This test is performed in following conditions such as:

Signs and symptoms of hyperthyroidism
• Weight loss
• Increased heart rate
• Anxiety
• Difficulty sleeping
Signs and symptoms of hypothyroidism
• Weight gain
• Dry skin
• Constipation
• Cold intolerance

Also Known As: Thyroxine, Tetraiodothyronine


Specimen Collected
  • Blood
Estimated Time Taken

Turnaround time for the T4 test is typically 1 business day.