| Sample Type | Blood |
| Usage/Application | Hospital |
| Size | 100 T |
| ICMR Approved | Yes |
| Country of Origin | Made in India |
Total T4 and free T4 are two separate tests that can help a doctor evaluate thyroid function. The total T4 test has been used for many years to help diagnose hyperthyroidism and hypothyroidism. It is a useful test but can be affected by the amount of protein available in the blood to bind to the hormone. The free T4 test is a newer test that is not affected by protein levels. Since free T4 is the active form of thyroxine, the free T4 test is thought by many to be a more accurate reflection of thyroid hormone function and, in most cases, its use has replaced that of the total T4 test. Whichever thyroxine measurement is ordered, it is usually ordered along with or following a TSH test. This helps the doctor to determine whether the thyroid hormone feedback system is functioning as it should, and the results of the tests help to distinguish between different causes of hyperthyroidism and hypothyroidism. Sometimes a T3 test will also be ordered to give the doctor additional diagnostic information. A T4 and TSH test may be ordered to help evaluate a person with a goiter and to aid in the diagnosis of female infertility. If a doctor suspects that someone may have an autoimmune-related thyroid condition, then thyroid antibodies may be ordered along with a T4 test. In those with known thyroid dysfunction, T4 and/or TSH tests may be ordered to monitor thyroid function. Newborns are commonly screened for T4 levels as well as TSH concentrations to check for congenital hypothyroidism, which can cause mental retardation if left untreated. A total T4 or free T4 test is primarily ordered in response to an abnormal TSH test result. Sometimes the T4 will be ordered along with a TSH to give the doctor a more complete evaluation of the adequacy of the thyroid hormone feedback system. These tests are usually ordered when a person has symptoms of hyperthyroidism or hypothyroidism. Signs and symptoms of hyperthyroidism may include: Increased heart rate; Anxiety; Weight loss; Difficulty sleeping; Tremors in the hands; Weakness; Diarrhea (sometimes); Light sensitivity, visual disturbances. The eyes may be affected: puffiness around the eyes, dryness, irritation, and, in some cases, bulging of the eyes. Symptoms of hypothyroidism may include: Weight gain, Dry skin, Constipation, Cold intolerance, Puffy skin, Hair loss, Fatigue, Menstrual irregularity in women. Severe untreated hypothyroidism, called myxedema, can lead to heart failure, seizures, and coma. In children, hypothyroidism can stunt growth and delay sexual development. Sometimes they are ordered as screening tests during routine blood testing, but expert opinions vary on who can benefit from screening and at what age to begin. In those with known thyroid disorders, the TSH and sometimes T4 are ordered at intervals to monitor the effectiveness of treatment. In pregnant women with thyroid disorders, the doctor is likely to order thyroid testing early and late in the pregnancy and for a time period following delivery to monitor the mother and baby. Thyroid hormone screening is commonly performed on newborns as part of newborn screening programs