What is the Origin of Levothyroxine Monotherapy?

The term combines 'Levothyroxine,' the pharmaceutical name for synthetic T4, with 'monotherapy,' signifying the use of a single agent. The foundation of this treatment lies in the physiological fact that T4 is the major secretory product of the thyroid gland, and most of the active T3 in the body is derived from the peripheral conversion of T4. Its clinical acceptance is based on decades of efficacy and safety data.

What is the Mechanism of Levothyroxine Monotherapy?

Once ingested, levothyroxine is absorbed and circulates as T4, binding to transport proteins. It serves as a prohormone, which is then peripherally converted into the biologically active hormone, triiodothyronine (T3), primarily by deiodinase enzymes in target tissues. The T3 then binds to nuclear receptors, modulating gene expression and regulating the body's overall metabolic rate, thus correcting the symptoms and biochemical abnormalities of hypothyroidism.

Levothyroxine Monotherapy

Meaning

Levothyroxine monotherapy is the standard clinical practice of treating hypothyroidism by administering the synthetic form of the thyroid hormone thyroxine, or T4, as the sole medication. This treatment aims to replace the deficient endogenous T4 production, restoring serum TSH and free T4 levels to their physiological reference ranges. It is considered the first-line and most common therapeutic approach for most forms of hypothyroidism.