While it may seem like sleep just happens (or doesn’t happen) at the end of each long day, the sleep you get is actually a result of specific biological processes. And though it can seem like physical exertion equals deep sleep, your sleep is more accurately attributed to hormonal changes that ebb and flow due to your circadian rhythms. While you sleep, certain hormones kick into gear, repairing and rebuilding, and preparing you for the coming day.

What Are Hormones?

Hormones are substances produced by glands that help regulate and control functions throughout your body. These hormones fluctuate to keep your body in balance (homeostasis), adjusting based on growth, your body's needs and more.

Hormones work around the clock unless an illness has impacted the secreting gland (or has been impaired or surgically removed). That means that even during sleep, hormones continue to work. And some even play a direct part in our sleep. Simeon Slavchev, Ph.D., chief assistant professor at the Faculty of Public Health, Bulgaria, says, “Hormones play a significant role in regulating our sleep-wake cycles. Hormones can influence the quality and duration of our sleep.”

Which Hormones Affect Our Sleep?

Several hormones fluctuate based on the circadian rhythm — the body’s internal sleep clock. The circadian rhythm is set by factors such as light and darkness, which are zeitgebers cueing our body about whether to be asleep or awake. Those cues trigger the release or suppression of hormones based on the light and dark schedule to create that sleepiness and wakefulness.

Hormones That Affect Sleep

Melatonin

Melatonin is the most well-known hormone associated with sleep — it’s the sleep hormone. Though marketed as a sleep supplement, melatonin is created naturally in the body and helps regulate sleep. Production increases when it gets dark, and the brain receives signals that it's time to sleep. Melatonin is not produced during the day when the brain receives signals that it is light and the sun is up. For people who work night shifts, the body may not have a consistent rhythm.

Thyroid-StimulatingHormone

Thyroid-stimulating hormone (TSH) is a hormone produced by the pituitary gland that regulates the thyroid gland function. It tells the thyroid whether or not to release triiodothyronine (T3) and thyroxine (T4). T4, the primary thyroid hormone, regulates how the body grows and creates energy. T3 plays a role in controlling the body’s metabolism. The highest quantity of TSH is released at night when people are asleep. While T3 and T4 aren’t directly related to sleep, they are directly impacted by the TSH released during sleep. When these hormone levels are not maintained, it can be an indication of thyroid disease. Sleep deprivation can lead to increased TSH levels, which impacts the T3 and T4 levels, potentially resulting in hypothyroidism.

Cortisol

Cortisol, the stress hormone, rises during the late stages of sleep. Cortisol levels are present throughout the day but gradually decrease as night approaches, ideally when the body is not stressed. Increased levels before bed can cause sleep disturbances. For most people, cortisol reaches its lowest point a few hours after bedtime and then starts climbing to reach its highest point by morning.

Growth Hormone

The growth hormone increases during and especially during deep sleep. GH fluctuates quickly, but its main functions are to produce protein and increase blood sugar levels. During childhood and adolescence, more GH is needed to help bones and tissues grow and repair. As we age and get older, production decreases. GH-releasing hormone, which prompts GH release, also stimulates sleep — mostly during the non-rapid eye movement cycles.

Sleep and sex hormones

Estrogen and progesterone

Estrogen and progesterone levels in the body fluctuate at various stages of life, most notably during puberty, pregnancy and menopause. These hormonal changes can have significant impacts on sleep patterns.

Progesterone has a sleep-inducing, calming effect and has helped with sleep latency and duration, as well as minimizing sleep disruptors.

Estrogen has a stimulating effect. Females are three times more likely than males to experience insomnia due to estrogen-related factors. Additionally, hormone replacement therapy and oral contraceptives may impact sleep by altering estrogen and progesterone levels.

Testosterone

Testosterone levels rise during puberty for both males and females and can have an impact on sleep. During this phase, girls may experience insomnia due to increased testosterone. In women, testosterone levels rise during menopause, while estrogen decreases and progesterone and other hormones fluctuate. In men, low testosterone levels have been associated with frequent night awakenings and disrupted, inconsistent sleep patterns. It's worth noting that testosterone therapy has been linked to sleep-breathing disorders like sleep apnea, and the risk may increase as men age.

Prolactin

Prolactin, a hormone released by the pituitary gland, plays a crucial role in breast milk production, breast development and various other body functions. Maintaining consistent sleep patterns is essential for proper prolactin secretion. Prolactin levels tend to surge during sleep, but sleep disruptions can interfere with this process. Sleep disturbances can have adverse effects on lactation, as well as on the reproductive function of both males and females.

Do Hormones Have a Positive or Negative Impact on Sleep?

So, now the question is, how do hormones impact our sleep? Hormones and sleep are directly related to each other in that sleep affects hormones, and hormones affect sleep. When one is out of balance, it can cause fluctuations across your body.

A healthy sleep routine will more likely lead to better hormone regulation. The opposite is also true: Poor sleep can lead to poor hormone balance. In both cases, this can lead to a cycle causing positive or negative outcomes until the cycle is broken.

Many of the hormones mentioned are directly related to circadian rhythms and work to keep the body in balance. When these hormones are too low or too high, the sleep cycles can be disturbed. In the same respect, sleep deprivation can cause hormonal imbalances. This also puts us at risk of diseases like diabetes, obesity, high blood pressure and heart disease.

How Can Hormonal Issues Affect Health?

When poor sleep disrupts hormones, many bodily functions can suffer, including fertility. Sleep deprivation has a negative impact on fertility in both men and women, including low testosterone in men. Women who suffer from poor sleep are found to have an increased risk of early miscarriage, inconsistent menstrual cycles, lack of ovulation, or infertility.

Sleep deprivation is shown to cause a larger decrease in testosterone as males age. Testosterone decreases with age normally, but sleep deprivation can magnify this problem. In the same respect, it is likely to cause a more significant decrease in estrogen in women, especially those who are postmenopausal. This suggests that sexual performance for both men and women of all ages decreases when hormones are low.

Along similar lines, prolactin levels can increase due to sleep deprivation. Prolactin rises in response to rising TSH levels and abnormal menstrual issues. The increase in prolactin may cause infertility. The increased TSH can lead to lack of or loss of menses, miscarriage, or low progesterone, which makes getting or maintaining pregnancy difficult. “Prolactin also helps regulate the immune system in addition to reproductive function,” says Slavchev.

Whose Sleep Might Be Affected More By Hormones?

While everyone will experience sleep issues that affect their hormones over the course of a lifetime, some people are more likely to notice the impact. Hormones naturally fluctuate throughout the lifespan and can alter sleep patterns when this occurs too. Times of illness, disease, or sleep deprivation are not the only times when hormone levels fluctuate.

“The impact of hormones on sleep can vary depending on a range of factors, including age, sex and health status,” says Slavchev. “For example, women may experience more significant fluctuations in hormone levels during the menstrual cycle, which can affect sleep quality. Similarly, individuals with sleep disorders such as insomnia may experience disruptions in hormone production and regulation.”

Altered hormones commonly affect:

• Women: In various stages of adulthood, hormones fluctuate, which can affect sleep, such as during pregnancy, menstruation and menopause.
• Adolescents: Puberty has a major impact on hormonal levels, particularly in females, which can alter sleep patterns for some time.
• Older adults: Aging causes a natural decrease in hormone production and sleep patterns.

What Causes Hormones To Change Related To Sleep?

When it comes to hormones and sleep, the two may not be separate issues. "Various factors affect sleep-related hormone levels: light exposure, stress and lifestyle choices like diet and exercise,” Slavchev says. “For instance, bright evening light can reduce melatonin, hindering sleep, while chronic stress increases cortisol, disrupting sleep patterns. Poor diet and inactivity can lead to imbalanced insulin and other hormones, impacting sleep quality."

When we sleep, our bodies are working to reset and prepare for the next day. Our hormones fluctuate up and down, working to create balance within our bodies. When our hormones cannot find balance or our sleep is not consistent, both elements can fall out of rhythm. As a result, a negative cycle of hormonal imbalance and poor sleep can occur. This can lead to poor health and several other issues that leave us feeling unwell.