Wickramasuriya Dilranjan S, Faghih Rose T
Annu Int Conf IEEE Eng Med Biol Soc. 2019 Jul;2019:11-14. doi: 10.1109/EMBC.2019.8857658.
Hormones play a fundamental role in homeostasis. We develop a state-space model relating the body's internal energy to cortisol hormone secretions. Cortisol is secreted in pulses and follows a 24 h circadian rhythm. Secretory event timings carry important information regarding internal feedback signaling taking place, as do the upper and lower serum cortisol levels. We relate an internal energy state variable to cortisol pulse timings and to the upper and lower serum cortisol envelopes. We derive Bayesian filter equations for state estimation and use the Expectation-Maximization algorithm for model parameter recovery. Results on multi-day simulated data show circadian energy variations in healthy subjects and non-circadian fluctuations throughout 24 h periods in patient models suffering from hypercortisolism. The results shed new light on why patients diagnosed with excess cortisol disorders frequently experience symptoms of daytime fatigue and sleep disturbances at night. The state-space model is also an important first step towards the design of closed-loop controllers for treating hormone-related disorders in a manner that closely emulates the body's own pulsatile feedback mechanisms.
激素在体内平衡中起着至关重要的作用。我们构建了一个状态空间模型，将身体的内部能量与皮质醇激素分泌联系起来。皮质醇以脉冲形式分泌，并遵循24小时的昼夜节律。分泌事件的时间以及血清皮质醇的上限和下限水平都携带了有关体内发生的内部反馈信号的重要信息。我们将一个内部能量状态变量与皮质醇脉冲时间以及血清皮质醇的上限和下限包络联系起来。我们推导了用于状态估计的贝叶斯滤波器方程，并使用期望最大化算法进行模型参数恢复。对多日模拟数据的结果显示，健康受试者存在昼夜能量变化，而患有皮质醇增多症的患者模型在24小时内存在非昼夜波动。这些结果为为什么被诊断患有皮质醇过多症的患者经常在白天感到疲劳和夜间出现睡眠障碍的症状提供了新的线索。状态空间模型也是朝着设计闭环控制器迈出的重要第一步，该控制器能够以紧密模拟身体自身脉动反馈机制的方式治疗激素相关疾病。
