Effects of the Restoration of Euthyroidism After Chronic Suppressive Therapy With Levothyroxine in Patients With Thyroid Cancer

Abstract

The main side effects of thyroid-stimulating hormone (TSH) suppressive therapy with levothyroxine (L-T4) are cardiac morphofunctional alterations and bone involvement. The objective of this investigation was to evaluate the reversibility of bone and cardiac alterations induced by chronic suppressive therapy after restoration of euthyroidism by reducing the L-T4 dose for a period of 12 months. Twenty patients were treated for thyroid cancer and maintained on TSH ≤0.1 mIU/L for a mean period of 7.5 years. After 1 year of TSH ranging between 0.5 and 4 mIU/L, normalization of all parameters was observed in the patient group. We conclude that even after prolonged exposure to suppressive therapy with L-T4, which is associated with cardiac morphofunctional alterations and changes in bone metabolism, a reduction of the L-T4 dose with consequent euthyroidism (normal TSH) can be associated with a reversal of these alterations.