Simulated profile of cortisol kinetics

Our dynamic model consists of (11.12) and (11.13). The physical meaning of the time delay in (11.12) is that the cortisol concentration c(t) affects other physiological parameters of the hypothalamic-pituitary-adrenal process (not present in equation 11.12), which in turn affect, via the feedback mechanism, cortisol concentration thereby cortisol controls its own secretion [438]. This cycle is postulated to last time t°, and that is how the concentration c° (t) at time t — t° arises. 

The value assigned to t° corresponds to about one cortisol secretion burst per hour in accordance with experimental observations [518]. The simulations were performed by a numerical solution of (11.12) and (11.13). This simulation exhibits the circadian rhythm, as well as the pulsatile nature of the cortisol secretion system. 

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