The five tests usually include TSH (thyroid stimulating hormone), T4 (thyroxine), T3 (triiodothyronine), FT4 (free thyroxine) and FT3 (free triiodothyronine). If a value on the test is followed by an upward arrow, it is elevated; if the arrow is downward, it is decreased. If FT3 and FT4 are elevated and TSH is decreased in the five tests, this indicates thyrotoxicosis. If FT3 and FT4 are decreased and TSH is increased, this indicates possible hypothyroidism. If one of the abnormalities is isolated, a comprehensive analysis based on medical history and symptoms is required. The causes of thyrotoxicosis are hyperthyroidism, subacute thyroiditis, autoimmune thyroiditis, etc. Therefore, if thyrotoxicosis is present, the cause needs to be further clarified and then treated accordingly. In the case of hypothyroidism, thyroid hormone supplementation or replacement therapy is usually required. The five tests of thyroid function can be evaluated and if certain values are abnormal, a clear diagnosis should be made by an endocrinologist in a timely manner and then treated accordingly.