They are the products of thyroid hormone synthesis, and T4 has one more iodine group than T3. Abnormal results of these two suggest abnormalities in thyroid function, but often are not directly related to clinical manifestations. Therefore, abnormal results of T3 and T4 need not be unduly concerned.

FT3 and FT4 (free T3 and free T4)

Free T4 is the most important hormone to play the thyroid function, and his abnormalities are often directly related to hyperthyroidism or hypothyroidism. The high or low according to FT4 results can be directly diagnosed with hyperthyroidism or hypothyroidism. Although accounting only for a small proportion of T4, FT4 has great impact, which can judge the outcome of thyroid function. FT3 is a good brother of FT4, they together play the role of thyroid hormones. According to FT3 and FT4 results which are high or low, you can directly determine the hyperthyroidism or hypothyroidism.

TSH (Thyroid-stimulating hormone)

The biggest feature of TSH is the opposite of FT3 and FT4, which the higher the FT3 / FT4, the lower the TSH. TSH is a sign of thyroid function - TSH is low, suggesting the upcoming hyperthyroidism; TSH is high, suggesting the upcoming hypothyroidism.