Modeling of testosterone regulation by pulse-modulated feedback

Area of Science:

• Endocrinology
• Mathematical Modeling
• Systems Biology

Background:

• Testosterone (Te) feedback regulation is crucial in the human male endocrine system.
• Existing models may not fully capture the complex dynamics observed in clinical hormone concentration profiles.

Purpose of the Study:

• To extend a hybrid (pulse-modulated) model of testosterone feedback regulation.
• To improve the model's agreement with clinical data by incorporating infinite-dimensional and nonlinear blocks.
• To develop a method for detecting gonadotropin-releasing hormone (GnRH) impulses.

Main Methods:

• Augmented a continuous hybrid model with infinite-dimensional and nonlinear components.
• Developed a linear least-squares optimization algorithm to detect GnRH impulses from luteinizing hormone (LH) concentrations.
• Utilized estimated impulse parameters to evaluate frequency and amplitude modulation functions.
• Identified all model parameters using Te and LH hormone concentrations.

Main Results:

• The enhanced model demonstrates improved agreement with clinical hormone concentration profiles.
• A robust method for detecting GnRH impulses from LH measurements was established.
• All parameters of the closed-loop system were successfully identified.
• Simulations of the estimated system mirrored clinical data behavior.

Conclusions:

• The proposed extended hybrid model accurately represents male testosterone feedback regulation.
• The developed algorithm effectively identifies GnRH impulses and parameters from hormone data.
• This approach offers a comprehensive tool for analyzing and understanding male endocrine feedback mechanisms.