Free thyroxine is a sensitive indicator of thyroid function in vitro, and it accurately reflects the function of the thyroid gland. Under normal circumstances, a woman’s free thyroid hormone may be elevated during the first trimester of pregnancy because of the compensatory increase in free thyroid hormone required for the development of the fetus after pregnancy and does not require treatment. Abnormal free thyroid hormone requires consideration of thyroid disorders, such as hyperthyroidism, which can lead to excessive release of free thyroid hormone in the blood, along with symptoms such as overeating, sweating, and weight loss. It is also seen in subacute thyroiditis, chronic thyroiditis, multinodular goiter, and diffuse toxic goiter, where the thyroid gland itself is damaged by inflammation and other factors, resulting in abnormal function and elevated free thyroid hormone in the blood. When free thyroid hormone is elevated, the patient’s diet should be supplemented with foods rich in iodine, such as nori and kelp. Patients with hyperthyroidism and other thyroid pathologies should be treated under the guidance of a doctor. They can take medications such as levothyroxine sodium to regulate the level of free thyroxine in the body, or use iodine-131 therapy or anti-thyroid drugs to inhibit the synthesis and release of thyroid hormones, and some patients may need to undergo surgery.