T3 usually refers to serum triiodothyronine, T4 refers to serum thyroxine, and TSH refers to thyroid stimulating hormone. Normal T3T4 and low TSH may be due to the presence of subclinical hyperthyroidism, and prompt medical attention is recommended. The presence of subclinical hyperthyroidism leads to abnormal thyroid function, making TSH more sensitive and its value can change rapidly. However, T3 and T4 do not have time to make changes, showing abnormal subclinical thyroid function status. When subclinical hyperthyroidism presents with clinical symptoms, it can be treated by using drugs such as methimazole. If T3T4 is normal and TSH is low, it is recommended that further examination be done to clarify the cause, and treatment should be carried out actively, and the use of drugs should be guided by the doctor.