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Circadian Entrainment Fidelity

Meaning

Circadian entrainment fidelity quantifies the accuracy and robustness with which an individual’s endogenous biological clock, centered in the suprachiasmatic nucleus, aligns itself with external environmental cues, primarily the light-dark cycle. High fidelity indicates a strong, stable synchronization of the internal 24-hour rhythms governing hormone secretion, metabolism, and sleep-wake cycles with the external world. Optimal hormonal health depends significantly on this precise entrainment, as misalignment can disrupt the rhythmic secretion of cortisol, melatonin, and growth hormone. This metric is a key indicator of systemic biological order and resilience.