Recent studies have shown that sleep disturbance reduces muscle protein synthesis by 18% and causes a 24% decrease in testosterone. Here is new evidence that once again explores the connection between sleep quality and hormone disruption.
Human hormone production is governed by circadian rhythms. A small cluster of cells in our body functions as a master clock that very intelligently orchestrates the switching on and off of the functions in all organs, body tissues and cells. This mater clock - the Suprachiasmatic nucleus (SCN) gets reset by the information it gathers from external light, in turn it resets all other ‘clocks’ involved in hormone homeostasis: the pineal gland, the pituitary gland and also communicates with the adrenal and gonadal glands to initiate hormone production.
Our sleep-wake cycle is mainly directed by the two hormones: cortisol and melatonin. However, recently scientists have been uncovering the roles of the endocrine hormones in the onset, duration and quality of sleep. Low testosterone levels in men, high estrogen levels in females and estrogen dominance in both sexes are all tightly intertwined with sleep.
The 24-hourly sleep-wake cycle in healthy people works like this: around 8.30pm the body starts secreting melatonin, which then peaks at 9.30-10pm. This is a good time to go to bed to prepare the body for relaxation and finally sleep. At this time the levels of cortisol subside to the lowest in the day. As we fall asleep, melatonin keeps getting produced through the night, around 5-5.30am the ratio of melatonin to cortisol flips back - cortisol starts getting secreted with the effect of lowering melatonin. By 6am the body is arousing due to the cortisol increase that peaks at about 8am and continues rising through the morning hours. These cycles of wakefulness and sleepiness are most apparent in the body that has a good habitual rhythm of going to bed and waking up approximately at the same time every day.
In people who have disrupted sleep, it has been noted that cortisol levels remain elevated through the night. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3649825/
Cortisol, called the stress hormone, has a direct and indirect effect on sleep. Its direct effect lies in its ability to keep the person awake late in the night through worrying or stressful thoughts, fear, anxiety, feelings of pressure from work demands, family or financial situation. The indirect effect occurs when sleep loss or disrupted sleep pattern influences the other hormones in the hypothalamic-pituatury-adrenal axis (HPA), such as adrenalin, adrenocorticotrophic hormone and norephinephrine by stimulating the body and causing hyperactivity.
The disorder in the production of melatonin and cortisol due to regular sleep disruption causes changes in the male and female sex hormones. Melatonin has a direct impact on production of testosterone and male reproduction function. https://www.dovepress.com/association-between-sleep-quality-and-semen-parameters-and-reproductiv-peer-reviewed-fulltext-article-NSS
Interestingly, testosterone and sleep quality have a bidirectional relationship. Recent studies have shown that the production of testosterone is dependent on the quality of sleep and its duration. In men testosterone levels typically reach the peak during the first three hours of uninterrupted sleep. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3955336/
Independently, low testosterone levels are associated with sleep problems such as nocturnal awakenings, poor sleep quality, and symptoms of depression. https://www.sciencedirect.com/science/article/pii/S0149763420305248. While testosterone production during the night is lower in ageing men due to biological changes associated with ageing, loss of sleep can be both the contributing factor and the result.
Female sex hormones and sleep are intricately linked and present a complex relationship. Worryingly, reported sleep disorders display a clear sex bias, where women are 41% more likely than men to experience insomnia, fatigue caused by lack of sleep, excessive daytime sleepiness. These health complaints only increase in ageing women.
In general women’s sleep disturbances are very pronounced during periods of life with significant hormonal changes. https://www.frontiersin.org/articles/10.3389/fnins.2020.625397/full Several studies report that young women start developing sleep problems as young as the time of their first menstrual cycle. It is believed that strong symptoms of PMS (premenstrual syndrome) become the factor that affects onset and quality of sleep. Thos suffering from PMS often report troubles falling sleep, morning fatigue and also rising anxiety problems.
Hormonal contraceptives (both estrogen and estrogen plus progestin) have a big impact on sleep quality, although the exact mechanisms are not fully understood. Pregnancy is also a period of dramatic hormonal changes that entail irregular sleep. Estrogen and progesterone concentrations increase as the fetus grows. After childbirth estrogen and progesterone start rapidly declining, and they return to normal about two or three months later. During the menopause, blood levels of estradiol (one of the three estrogen hormones) and progesterone fall dramatically, as it happens sleeping problems become a very common complaint. Interestingly, compared to premenopausal women, postmenopausal women tend to report more of their trouble falling and staying asleep, difficulty sleeping, nighttime awakenings, and daytime drowsiness.
Is there one of the female sex hormones dominating sleep regulation? A big body of evidence suggests that it is not estrogen or progesterone that are to blame, but the fluctuations of these hormones at various stages of biological development in women. For example, the times when progesterone levels are high, such as the luteal phase of the menstrual cycle (roughly the middle of the cycle) and also the transition to the menopause show increased incidence of sleep problems. Periods of change in estradiol levels (a type of estrogen) are also linked with irregular sleep. https://www.frontiersin.org/articles/10.3389/fnins.2020.625397/full
So which of the two should come first? Hormone regulation and a healthy sex hormones balance or sleep quality?
A study last year demonstrated that in healthy young men one night of sleep deprivation caused a 24% decrease in blood testosterone levels, as well as a 21% increase in cortisol levels. But perhaps the most significant result was the reduced muscle protein synthesis - by 18%. https://physoc.onlinelibrary.wiley.com/doi/full/10.14814/phy2.14660
A group of men who previously did not have any sleep problems and were healthy were kept awake through one night. The researchers took blood samples at the start of the experiment, throughout the night, in the morning and in the afternoon following a night of wakefulness. Even though the men were allowed to have small snacks (such as fruit) if they were hungry and were fed a healthy breakfast early in the morning, following a sleepless night their muscle protein synthesis was decreased by 18%.
Skeletal muscle is a good indicator of health in a human body. Loss of muscle mass in older age is a strong risk for all cause mortality. Skeletal muscle regulates our metabolism. Sarcopenia, loss of muscle due to ageing, is a hallmark and a precursor to a wide range of conditions, such as neuromuscular disease, frailty, obesity and type 2 diabetes. These conditions are reported to be 15-30% higher in people who experience sleep deprivation or inverted sleep cycles regularly. As sleep loss affects metabolism, the amount of quality sleep contributes to the maintenance of fat-free body mass and regulation of blood sugar levels.
One cannot examine one body function in isolation to the others, and sleep and hormone production is one such example. As I was doing research on this subject, it became more and more clear to me that hormone production is rather out of our control, whereas sleep is. Improving sleep quality and working on one’s good sleep habits should be paramount for getting one’s hormones regulated and balanced.
