What does t4 mean? t4 is a hormone synthesized by the thyroid gland that promotes growth and development, thermogenesis, and is involved in sugar, fat, and protein metabolism. The t4 is the serum total thyroxine, and the normal thyroxine in adults is 64~154 nmol/L. Clinically elevated thyroxine can be seen in hyperthyroidism, painless thyroiditis, subacute thyroiditis and so on. It can be manifested as symptoms such as fear of heat, hand tremor, panic, and agitation. Reduced thyroxine can be seen in pituitary hypothyroidism, chronic thyroiditis, cretinism and so on. It can be manifested as fear of cold, low mood, and so on. When abnormal lab results occur, it is necessary to actively consult the doctor and follow the doctor’s instructions for reasonable treatment.