Integrated iodine biokinetic models for pregnancy and lactation based on the ICRP reference adult model

Exposure to radioactive iodine (radioiodine) during pregnancy and lactation poses unique risks to both mothers and their offspring due to altered iodine metabolism and heightened radiosensitivity. Existing biokinetic models, such as those developed by Berkovski, have provided a foundation for understanding iodine kinetics in these physiological states but lack integration with the latest International Commission on Radiological Protection (ICRP) reference model for non-pregnant adults. In this study, we developed integrated biokinetic models for pregnancy and lactation that are structurally consistent with the ICRP Publication 137 adult iodine model. Our models account for physiological changes in renal clearance, thyroid hormone production, and iodide uptake during pregnancy, and incorporate fetal compartments for transplacental iodine transfer. The lactation model introduces a breast milk compartment to reflect iodine excretion via nursing, using observed transfer factors and milk production rates. Model predictions were validated against clinical data and compared with outputs from the Berkovski model. The proposed models demonstrated improved agreement with observed iodine concentrations in maternal blood, placenta, amniotic fluid, and breast milk, offering more accurate predictions of iodine biokinetics within the maternal body and its lactational excretion. This integrated framework allows for consistent dose estimation across non-pregnant, pregnant, and lactating states, providing a valuable tool for internal dose assessment and radiation risk analysis in vulnerable populations. Future applications include the calculation of absorbed dose coefficients for maternal and fetal organs following radioiodine exposure.