Complex dynamic phenomena in a low-order model of non-basal testosterone regulation

Complex nonlinear dynamics in a recent mathematical model of non-basal testosterone regulation are investigated. In agreement with biological evidence, the pulsatile (non-basal) secretion of testosterone is modeled by frequency and amplitude modulated feedback. It is shown that, in addition to already known periodic solutions with one and two pulses in the least period of the closed-loop solution, cycles of higher periodicity and chaos are present in the model in hand. The broad range of exhibited dynamical behaviors makes the model highly promising in model-based signal processing of hormone data.