Levothyroxine (T4) combined with Liothyronine (T3) is used in thyroid hormone replacement therapy to restore normal metabolic balance in patients with hypothyroidism and related thyroid disorders. This combination provides both the long‑acting stability of T4 and the rapid, active effects of T3, ensuring a more physiological hormone profile. It is particularly prescribed when patients do not respond adequately to levothyroxine alone, as adding liothyronine can improve energy, mood, and cognitive function. Clinically, this dual therapy helps manage symptoms such as fatigue, weight changes, and slowed metabolism by mimicking the natural secretion of thyroid hormones. It may also be used in cases of goiter management, thyroid cancer suppression, and certain diagnostic procedures where precise hormone regulation is required. By balancing both hormones, the therapy supports cardiovascular health, neurological activity, and overall metabolic regulation, offering a comprehensive approach to thyroid hormone replacement under medical supervision.