arXiv:2611.13277v1 Announce Type: new Abstract: An impulsive model of endocrine regulation equipped with frequency- and amplitude-modulated pulsatile feedback is extended to study the dynamical effects pertaining to limitations due to the releasable hormone pool. The model describes a three-hormone regulatory loop and is applicable to endocrine systems such as the reproductive, stress, and growth hormone axes. Conditions guaranteeing the existence and uniqueness of a periodic solution with a single feedback-triggered impulse per period (a 1-cycle) are derived, together with monotonicity properties of its characteristics. An explicit Jacobian formula is obtained to assess local orbital stability. Model analysis demonstrates that a reduced hormone-pool replenishment rate produces a lower-amplitude, higher-frequency 1-cycle. This behavior is consistent with experimentally observed alterations in testosterone regulation in aging human males.