What is the Origin of Combination Therapy T4/T3?

The strategy is derived from the fundamental physiological understanding that the human thyroid gland secretes both the prohormone T4 and a smaller, yet significant, amount of the active hormone T3. The use of combination therapy represents an evolution in thyroid management, acknowledging that relying solely on peripheral T4-to-T3 conversion is not sufficient for all individuals.

What is the Mechanism of Combination Therapy T4/T3?

The T4 component provides a stable, long-acting reservoir of prohormone, ensuring a steady state of circulating thyroid hormone. The T3 component directly supplies the active hormone, bypassing potential genetic or acquired defects in the peripheral deiodinase enzymes responsible for T4-to-T3 conversion. This dual delivery mechanism aims to restore both systemic and cellular euthyroidism by providing a more complete and bioavailable hormonal replacement.

Combination Therapy T4/T3 ∞ Area

Combination Therapy T4/T3

Meaning

Combination Therapy T4/T3 is a clinical approach to managing hypothyroidism that involves the simultaneous administration of synthetic levothyroxine (T4) and liothyronine (T3) to more closely replicate the thyroid gland’s natural secretory output. This regimen is often considered for patients who continue to experience debilitating hypothyroid symptoms despite achieving a normal TSH level on T4 monotherapy. The therapeutic objective is to ensure optimal T3 availability at the cellular level, which is the biologically active hormone.