Born & Fehm (2000) in Endocrine Reviews provide an overview of the interaction between sleep and the endocrine system. Their central point: sleep is not a passive state, but an actively regulated process closely linked to hormonal rhythms. Many hormones follow a circadian pattern and are specifically influenced by different sleep phases, particularly deep sleep (slow-wave sleep).

The authors describe how the hypothalamus-pituitary-adrenal axis (HPA axis), growth hormone, prolactin, melatonin, and cortisol are interconnected with sleep architecture. For instance, growth hormone is primarily released during the first cycles of deep sleep, which is important for recovery and metabolism. Cortisol, on the other hand, drops in the early night and rises towards morning. Sleep disruption—due to stress, shift work, or sleep deprivation—can disrupt these rhythms and lead to elevated cortisol levels, reduced insulin sensitivity, and other metabolic consequences. The article also emphasizes the role of sleep in memory, immune function, and energy balance via hormonal pathways. Chronic sleep disruption can contribute to obesity, mood disorders, and impaired stress regulation. Conversely, hormonal changes (for example, due to stress or illness) can disrupt the sleep structure itself, which can create a vicious cycle.

Born and Fehm conclude that healthy sleep is essential for endocrine stability. Sleep deprivation or fragmentation impacts multiple hormonal systems and thereby affects both physical and mental health. The article underscores that sleep and hormonal regulation should be viewed as one integrated system, not as separate processes.