To : Carolyn Zara Re : Graves Disease The decision to ablate the thyroid is a tricky decision that requires an experienced endocrinologist. However, several options are available but must be evaluated for their usefulness by the clinician at hand. Propylthiouracil (PTU) has been used in thousands of breastfeeding women and is known to be quite safe. Just ocassionally evaluate the infants' thyroid status if you are uneasy about the medication. Do not use methimazole. If radioactive I-131 is used, the breastfeeding mother should discontinue breastfeeding for 7-14 days prior to exposure for two reasons. First I-131 concentrates in breastmilk and can increase the infants risk of future thyroid cancer and maybe even damage the infants thyroid. In addition, approximately 28% of the radioactive iodine dose administered to the mother will concentrate in the lactating breast tissue, and may theoretically increase the risk of breast cancer. But we all know that thyroid function sometimes go ary during and after pregnancy. Its seems reasonable to wait and try other therapy before destroying the thyroid completely. But this still depends on the clinical situation at hand. Tom Hale