Modeling of testosterone regulation by pulse-modulated feedback

Abstract

The continuous part of a hybrid (pulse-modulated) model of testosterone (Te) feedback regulation in the human male is extended with infinite-dimensional and nonlinear blocks, to obtain the dynamics that better agree with the hormone concentration profiles observed in clinical data. A linear least-squares based optimization algorithm is developed for the purpose of detecting impulses of gonadotropin-releasing hormone (GnRH) from measured concentration of luteinizing hormone (LH). The estimated impulse parameters are instrumental in evaluating the frequency and amplitude modulation functions parameterizing the pulse-modulated feedback. The proposed approach allows for the identification of all model parameters from the hormone concentrations of Te and LH. Simulation results of the complete estimated closed-loop system exhibiting similar to the clinical data behavior are provided.