Breast milk content of 131I in a hypothyroid patient

An oral dose of 185 MBq of 131I (sodium iodide) was administered to a lactating mother for whole body scanning. Breast milk was collected at several points in time, and assayed for radioactivity. The radioiodine concentration in the milk was found to be 4 MBq/dL at 6 h (about 2% of the dose). The radioactivity in breast milk decreased with a biological half-life of about 15 h in this hypothyroid patient. Following ingestion of radioiodide (such as [131I]sodium iodide), the appearance of radiolabel in breast secretion has been well documented. However, data do not appear in the literature on this process in the grossly hypothyroid state. We, therefore, are reporting our experience with such a situation.