To the Editor.
—We read with interest the article by Freeman et al1 and the accompanying editorial by Goldman2 in the July 1986 issue of the Archives concerning postpartum thyroid dysfunction. It was stressed that the radioactive iodine uptake test of the thyroid is the test of choice to separate thyrotoxicosis due to stimulation from that due to destruction. However, the radioactive iodine uptake test performed with iodine 131 is contraindicated during breast-feeding. Alternatively, an iodine 123 uptake test has been recommended, but a period of five to seven days of artificial bottlefeeding is needed to avoid significant irradiation of the infant's thyroid gland.3 In our experience, discontinuing breast-feeding for five to seven days will add stress to the motherchild relationship and is, therefore, not acceptable.A high correlation between the 24hour iodine 131 uptake of the thyroid and the 20-minute technetium Tc 99m pertechnetate uptake test