T4 Suppression Therapy Post Radiation Exposure


Question

A 65 year old white female with history of irradiation as an infant, apparently as a treatment for an enlarged thymus. The patient has been on T4 suppression therapy since age 20. Thyroid function tests show normal T4 and suppressed TSH, compatible with her treatment goals. Thyroid gland is non-palpable and the latest thyroid ultrasound done three months ago showed no evidence of thyroid nodules. The patient otherwise is asymptomatic, with no history of documented osteoporosis and no history of atrial fibrillation. Should this patient continue to be on T4 suppression therapy?

Thank you, and best regards. Ahmad A. Tarhini, MD,Internal Medicine Resident

University of Pittspurgh Medical Center,Mckeesport Hospital

Response

Your question is an excellent one, but there is no answer that is proven to be correct. It is hard to believe that after nearly 60 years that a neoplasm could suddenly begin. One thinks more likely such mutational events happen near the time of the radiation, and slowly grow over the years. The fact that her exam and US are normal is also supportive of stopping treatment. Thus the risk of stopping medication must be very low, especially if you do a follow exam and US annually. On the other hand, if her heart and bones are perfect, and her TSH is at the bottom end of normal ( not truly suppressed) below normal, it would also seem that the risk of continuing treatment in this patient is negligible.I think I would finally end on the side of cautiously continuing

treatment, so long as there are no contraindications.

Leslie J De Groot,MD