1. A simulation system for simulating a function of a biological organ associated with diabetes, the simulation system comprising: a computer readable storage medium having stored therein instructions executable by a processor for performing the steps of: storing a mathematical model that comprises a plurality of parameters and represents a function of a biological organ associated with diabetes; receiving input of time-series actual measurement data representing blood glucose and/or blood insulin levels obtained by measuring the biological response of a subject; estimating data representing blood glucose and/or blood insulin levels of the subject at a time point that is different from the time-series actual measurement data, generating time-series reference data representing the biological response of the subject based on the time-series actual measurement data and the estimated data; acquiring a plurality of sets of parameter values of the mathematical model; comparing each virtual biological response generated when each of the plurality of sets of parameter values is applied to the mathematical model with the generated time-series reference data; and selecting one of the plurality of sets of parameter values based on the comparison so as to generate a plurality of parameter values wherein the mathematical model for the subject represents the function of the biological organ when the plurality of parameter values are applied to the model.