Levothyroxine is chemically identical to thyroxine (T4), which is naturally secreted by the follicular cells of the thyroid gland. It is used to treat thyroid hormone deficiency, and occasionally to prevent the recurrence of thyroid cancer. It has been shown that some people are allergic to some of the inactive ingredients found in the commericial brands of Levothyroxine, Oroxine and Euroxsig.Our T4 capsules do not contain binders and are used as a safe and effective alternative. Prescription only product - please mail, email, or fax prescription prior ordering.