Circadian Rhythm

Circadian rhythms are endogenous, approximately 24-hour oscillations in physiological and behavioural processes driven by molecular clock genes in the suprachiasmatic nucleus (SCN) of the hypothalamus. The core clock mechanism involves transcription-translation feedback loops of genes including CLOCK, BMAL1, PER, and CRY. These rhythms regulate the timing of hormone secretion, including melatonin, cortisol, and growth hormone, with the largest growth hormone pulses occurring during slow-wave sleep in the first half of the night. Circadian disruption from shift work, jet lag, or chronic sleep deprivation has been linked to metabolic syndrome, impaired immune function, accelerated ageing, and reduced tissue repair capacity. Peptide timing is increasingly recognised as relevant in research protocols because peptides that stimulate growth hormone release, such as CJC-1295 and Ipamorelin, may produce optimal responses when administered in alignment with the natural circadian GH pulse. Maintaining circadian integrity supports autophagy, mitochondrial function, and sirtuin activity.