A delay-differential equation model of the feedback-controlled hypothalamus–pituitary–adrenal axis in humans

The present work develops and analyses a model system of delay-differential equations which describes the core dynamics of the stress-responsive hypothalamus–pituitary–adrenal axis. This neuroendocrine ensemble exhibits prominent pulsatile secretory patterns governed by nonlinear and time-delayed feedforward and feedback signal interchanges. Formulation and subsequent bifurcation analysis of the model provide a qualitative and mathematical frame work for a better understanding of the delayed responsive mechanisms as well as the dynamic variations in different pathological situations.