Sleep isn't a luxury – it's a biological necessity. Just like a healthy diet and regular exercise, getting enough quality sleep is fundamental for overall health. Despite this, in the United States alone, about one-third of adults don't get the recommended amount of nightly rest.
Getting to the root of this problem may lie in hormonal balance. Fluctuations and imbalances can disrupt our ability to achieve a restful night's sleep. By understanding the hormonal connection to the sleep cycle, we can take steps to promote better sleep.
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Understanding Sleep and Hormonal Regulation
Sleep is a complex process essential for all aspects of health. It is characterized by distinct stages and influenced by the body's internal clock, known as the circadian rhythm.
The circadian rhythm is the body's 24-hour cycle governed by the suprachiasmatic nucleus (SCN) in the brain's hypothalamus. Nearly every tissue in the human body has its own circadian rhythm. Circadian rhythms influence sleep patterns, hormone and neurotransmitter release, digestive function, and body temperature over the course of a day. (16)
The SCN receives input from light-sensitive cells in the retina to synchronize the body's internal clock with external environmental cues. By coordinating the secretion of hormones like melatonin and cortisol, the circadian rhythm ensures the appropriate timing of sleep and wakefulness.
A typical sleep cycle is 90 minutes and consists of four total stages, broadly categorized as either non-rapid eye movement (NREM) or rapid eye movement (REM).
NREM Sleep
NREM sleep is divided into three phases. Stage 1 marks the transition from wakefulness to light sleep. As you transition to Stage 2, brain waves slow down with occasional bursts of rapid brain activity known as sleep spindles. Stage 3 is deep, restorative sleep required for growth, repair, cognitive function, and memory. (46)
REM Sleep
Rapid eye movements, brain activity similar to wakefulness, and vivid dreaming characterize REM sleep. Muscles enter a temporary state of paralysis, heart rate and blood pressure increase, and breathing patterns become irregular. REM sleep is essential for cognitive function, memory consolidation, and emotional processing. (46)
Key Hormones That Affect Sleep
This coordinated secretion of melatonin and cortisol by the body's circadian rhythm ensures that we experience restful sleep at night and are alert during the day.
Melatonin: The Sleep Hormone
Melatonin is a hormone produced by the brain's pineal gland in response to darkness. It is called the "sleep hormone" because it induces sleepiness. The body begins producing melatonin in the evening as the sun goes down. Melatonin production peaks about seven hours after sunset. As the sun rises in the morning, light suppresses melatonin production to undetectable levels. (7, 31)
Supplemental melatonin can be used to treat sleep disorders and mitigate the effects of jet lag. The benefits of taking melatonin close to an individual's desired bedtime include preventing/reducing jet lag, increasing total sleep time, reducing sleep onset time, and improving sleep quality. (1, 25, 27)
Cortisol: The Stress Hormone
Cortisol, produced by the adrenal glands, follows an opposite secretion pattern from melatonin. Cortisol begins to rise in the morning, reaching its peak between 7-8 a.m., and then gradually decreases throughout the day until it is at its lowest between 2-4 a.m. (37)
Because cortisol stimulates alertness, elevated nighttime cortisol levels can interfere with getting sound sleep. Stress, which increases cortisol levels and can interfere with its regular secretion pattern, is associated with difficulty sleeping and reduced time spent in deep and REM sleep. (9, 17)
Meditation is one technique for relieving stress before bedtime. Meditation counteracts the stress response, reduces cortisol levels, and improves sleep quality by triggering mental, emotional, and physical relaxation.
Hormonal Imbalances and Sleep Disorders
Circadian rhythm disruptions can interfere with normal hormonal secretion patterns, contributing to hormonal imbalances. For example, low testosterone levels are often measured in shift workers.
This relationship becomes even more complex, however, because hormonal imbalances often manifest as trouble sleeping. When hormones are not within an optimal range, they can result in changes to sleep architecture, increased arousal, and psychological and physical symptoms that interfere with going or staying asleep.
Thyroid Hormones
The thyroid is a butterfly-shaped gland in the neck that produces the hormones T3 (triiodothyronine) and T4 (thyroxine). These hormones regulate metabolism – how the body uses energy. Thyroid disorders, including hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid), are risk factors for sleeping troubles.
Up to 72% of people with hyperthyroidism experience sleep disorders. This may be due to hyperarousal, anxiety, and sweating associated with excessive thyroid hormones that interfere with the ability to sleep. (35)
Hypothyroidism is a risk factor for sleep apnea, characterized by frequent waking during the night. At the same time, hypothyroidism often causes excessive fatigue and may lead to hypersomnia (excessive sleepiness). (35)
Growth Hormone
Growth hormone is a hormone made by the pituitary gland in the brain. Roles of growth hormone include:
- Stimulating bone and muscle growth
- Repairing tissues
- Promoting metabolism
- Regulating blood sugar
The body releases pulses of growth hormone during deep sleep. This is why getting enough sleep is especially important for children and adolescents who are still growing. Studies have shown that chronic sleep deprivation can significantly suppress growth hormone production. A single night of poor sleep can reduce growth hormone by as much as 70%.
Acromegaly is a rare condition caused by excess growth hormone, leading to abnormal bone and tissue enlargement. It is often associated with obstructive sleep apnea, caused by upper airway obstruction due to enlargement and thickening of the tongue and throat.
Estrogen and Progesterone: Reproductive Hormones
Estrogen is a hormone primarily produced by the ovaries and, in smaller amounts, by the adrenal glands and fat tissue. Its roles are most notably related to the reproductive system, but estrogen also impacts sleep through its associations with body temperature regulation, neurotransmitter metabolism, and maintenance of deep sleep. (30)
Progesterone is another sex hormone that maintains pregnancy. Progesterone has a mild sedative effect because it inhibits glutamate (an excitatory neurotransmitter) and potentiates GABA (an inhibitory neurotransmitter) in the brain.
Fluctuations in estrogen and progesterone can influence a woman's ability to sleep, such as during menstruation, pregnancy, and menopause (12). Low estrogen increases the risk of developing sleep apnea, and low levels of progesterone can cause insomnia.
Testosterone: The Androgen Hormone
Testosterone is the sex hormone associated with male reproductive function. Like cortisol, testosterone levels peak in the morning and decline gradually throughout the day (47). Sleep deprivation can lead to reduced testosterone production. This is because deep sleep triggers the release of gonadotropin-releasing hormone (GnRH), which in turn stimulates testosterone production.
Testosterone levels can also influence sleep quality. High testosterone, such as that caused by testosterone replacement therapy (TRT), is linked to an increased risk of sleep apnea. Conversely, low testosterone is associated with sleep problems like difficulty falling asleep, staying asleep, and decreased deep sleep.
Optimizing Hormonal Health for Better Sleep
Given the intricate relationship between hormones and the sleep cycle, diagnosing and correcting hormonal imbalances can be one aspect of a comprehensive treatment plan to optimize sleep for those having problems sleeping.
Lifestyle and Dietary Strategies
Creating a healthy lifestyle can go a long way in supporting hormonal balance and promoting restful sleep. Here are some adjustments to consider:
Create a Consistent Sleep Schedule: Our bodies thrive on routine. Go to bed and wake up at the same time each day, even on weekends. This helps regulate the natural sleep-wake cycle, making falling asleep and waking up easier. (44)
Embrace Natural Light: Sunlight is a natural cue for your circadian rhythm. Get regular morning exposure to sunlight, ideally within the first hour of waking. This helps suppress melatonin and stimulates cortisol production in the daytime, making you feel more alert.
Avoid Blue Light: In the evening, dim the lights and avoid exposure to screens that emit blue light, such as smartphones, computers, and televisions. Blue light suppresses melatonin production and can interfere with sleep. (38)
Move Your Body: Regular physical activity is a win-win for hormones and sleep. Exercise helps manage stress hormones like cortisol, which can otherwise disrupt sleep. Aim for at least 30 minutes of moderate-intensity exercise most days of the week. However, avoid strenuous workouts close to bedtime, as they can be stimulating. (22, 40, 57)
Dietary Do's and Don'ts: Prioritize a balanced diet rich in fruits, vegetables, whole grains, and lean proteins. These foods provide essential nutrients that contribute to hormonal health and sleep regulation. Excessive sugar and caffeine intake can disrupt blood sugar levels and have a stimulating effect. Minimize sugar intake and limit drinking caffeinated drinks to the mornings.
When to Seek Professional Help
While occasional sleep troubles can be normal, persistent sleep problems may be a sign of an underlying hormonal imbalance. Here are some symptoms that warrant a consult with your doctor:
- Significant changes in your usual sleep habits, like difficulty falling asleep, staying asleep, waking up much earlier than intended, or experiencing frequent nighttime awakenings
- Premenstrual syndrome (PMS)
- Irregular menstrual cycles
- Night sweats and hot flashes
- Mood swings, depression, and anxiety
If your doctor finds evidence of a hormonal imbalance affecting your sleep, they can recommend personalized treatment options based on the underlying cause. These may include lifestyle changes, medications and supplements for sleep disorders and hormonal imbalances, and hormone replacement therapy.
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Key Takeaways
Sleep and hormones are intricately linked. By understanding how hormones influence sleep quality (and vice versa), we can take proactive steps to promote hormonal balance and achieve restful nights simultaneously. A combination of lifestyle and dietary adjustments can go a long way to create a foundation for healthy sleep. If you suspect a hormonal imbalance might be disrupting your sleep, don't hesitate to consult your doctor.
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