Data analysis and evaluation. The data generated by this pilot-trial will be used to construct pharmacokinetic curves of tracer appearance and clearance in the collected samples (total plasma, plasma PII-fraction, plasma PBI-fraction, urine, stools). Curves will be constructed by fitting a LOESS multiple regression model, a non-parametric locally weighted scatter plot smoothing of tracer concentration in samples as a function of time, and provide uncertainty range to visually represent the tracer's pharmacokinetic patterns and variability of response. For the evaluation of tracer kinetic patterns we will generate classic pharmacokinetic modelling parameters, including maximum tracer concentration (cmax), time at maximum tracer concentration (Tmax), elimination rate constant (ke), absorption rate constant (ka), and area under the curve (AUC), by using the simulation analysis and modelling software SAAM II (University of Washington). Total tracer retention will be calculated as total tracer intake - total tracer excreted (AUCurine + AUCstool). Total tracer absorption will be calculated as total tracer intake - total tracer appearance as plasma inorganic iodine (AUCPII). The optimization of procedures for routine application of this method will mainly include the definition of minimal requirements of specimen's specific sampling duration (number of days) after the administration of the tracer dose. This will be assessed by using ROC curves.