To : Mary Kay
Re : Radioactive Iodine-131

Doses of I-131 sufficient to ablate or destroy thyroid tissue are most
certainly high enough to injure a breastfed infant and potentially the
breast tissue.   About 40% of the dose will transfer into human milk, and
about 45% will transfer to the thyroid.  Although the published literature
varies,  it is my personal opinion, that a breastfeeding mother should
discontinue breastfeeding for at least 2 weeks prior to treatment with I-131
so that she will have time to dry up.  Iodine can concentrate in breast
tissue and the radiation dose to the breast can be excessively high.

I know that some references say that one can begin breastfeeding at after 14
days,  but I believe these are wrong, as they did not take into account the
amount of radiation in the "trough" of the curve, which can be high.  I
would suggest you read the references listed in my book.





Regards

Tom Hale, R.Ph., Ph.D.

http://neonatal.ttuhsc.edu/lact/