Sequential Amniotic Fluid Thyroid Hormone Changes Correlate with Goiter Shrinkage following in utero Thyroxine Therapy.

Several isolated reports of fetal goiter treatment have shown limited generalizability of approaches and provide no real guidance for optimal timing, dosages, and treatment strategies. Graves' disease accounts for >60% of these cases. Maternal treatments of hyperthyroidism include antithyroid medications such as methimazole and more commonly propylthiouracil (PTU). Here, our management of a patient with a fetal thyroid goiter from maternal exposure to PTU diagnosed at 23.6 weeks' gestation and the management of other cases allow us propose a general strategy for treatment. Intrauterine therapy with 200 and then 400 μg of levothyroxine (3 weeks apart) showed an 85% reduction in fetal thyroid goiter volume. We collected amniotic fluid samples at the time of treatments and assayed thyroid hormones and associated antibodies which closely reflected the changes in thyroid goiter mass volume. Our observations suggest a weekly or biweekly therapeutic intervention schedule. Utilizing both goiter size as well as a novel approach in using amniotic fluid hormone levels to monitor therapy efficacy might improve the quality of treatments. Only with a standardized approach and collection of amniotic fluid thyroid panels do we have the opportunity to develop the database required to determine the number and timing of treatments needed.