Radiation dosimetry from breast milk excretion of radioiodine and pertechnetate.

Measurements were made of the activity in samples of breast milk obtained from a patient with postpartum thyroiditis following administration of [123I]sodium iodide and subsequently [99mTc]pertechnetate 24 hr later. Both 123I and 99mTc were found to be excreted exponentially with an effective half-life of 5.8 hr and 2.8 hr, respectively. Less than 10% of the activity was incorporated into breast-milk protein. After administration of [123I]sodium iodide breast feeding should be discontinued for 24-36 hr to reduce the absorbed dose to the child's thyroid.