The body’s circadian rhythm is a 24-hour clock that governs sleep and wake cycles, and is aligned with environmental light and darkness. Circadian rhythms can impact various physiological processes, including sleep quality, energy production, and hormonal balance. Studies have linked circadian rhythm to control of melatonin, cortisol, insulin, and various other hormones. There’s a growing interest in functional medicine in better understanding just how circadian rhythms impact how hormones function, and how regulation of circadian rhythm can play a role in optimizing hormone health.  

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What is Your Circadian Rhythm?

Your circadian rhythm is a 24-hour internal clock that responds to light changes in your environment, regulating various parts of human physiology including your sleep-wake cycle, metabolism, and production of hormones.  This rhythm helps humans adapt to changes in their environment, and optimize energy levels and expenditure accordingly. Within the brain, a small area of the hypothalamus called the suprachiasmatic nucleus (SCN) controls circadian rhythm. The SCN is directly affected by light exposure, and goes on to impact hormone production accordingly, producing melatonin or cortisol to set the sleep-wake cycle. 

The sleep-wake cycle that is governed by circadian rhythms can influence digestion, body temperature, eating habits, and hormone release, making these rhythms essential for overall health. Disruptions in the circadian rhythm have been linked to obesity, anxiety, impaired glucose metabolism, depression, fatigue, and loss of concentration, amongst other conditions, demonstrating the wide-reaching effect of these rhythms on physiology.  

The Link Between Circadian Rhythms and Hormonal Health

Circadian rhythm controls the production of various hormones, including melatonin, cortisol, insulin, glucagon, estrogen, leptin, and others. These hormones also serve as feedback signals to regulate the circadian rhythm, meaning that hormone imbalances can negatively impact circadian rhythm as well. Disruptions in circadian rhythm can lead to impaired glucose and lipid metabolism, changes in cortisol and melatonin production, and can further impact hormones by impacting hunger-satiety signaling and eating behaviors.  

Cortisol and melatonin are two hormones that are synced directly by circadian rhythm signaling. With a healthy circadian rhythm, cortisol is secreted in the morning to help wake up the body, and slowly decreases in production as the day goes on.  In the evening when darkness predominates, melatonin rises to help with sleep as cortisol drops off. Circadian disruptions can lead to reversals of the cortisol-melatonin rhythm, causing daytime fatigue and drowsiness as well as trouble falling and staying asleep.

Circadian rhythm also influences production of sex hormones such as estrogen, progesterone, testosterone, and gonadotropins. In women, circadian rhythm impacts sex hormone production differently across the menstrual cycle, with more regular regulation occurring in the follicular phase of the cycle. Studies of shift workers have suggested that the disruption of circadian rhythms that occurs with shift work is a factor contributing to impaired reproductive function of female shift workers that has been observed.  

Common Disruptors of Circadian Rhythms

There are several different lifestyle and environmental factors that can disrupt the circadian rhythm, including:

• Exposure to artificial light that isn’t aligned with natural daylight hours, such as blue light exposure after dark
• Meal timing, with late night eating being particularly disruptive to circadian regulation of hormones
• Irregular sleep patterns, commonly seen in shift workers
• Social jet lag due to work or school schedules

Short-term impacts of circadian rhythm disruption on hormone health may include increased reactivity to stress, emotional symptoms such as anxiety, and poor glucose regulation. Cognitive and memory deficits such as trouble concentrating or trouble remembering things may also occur. Sleep may also be disrupted as acute changes in circadian rhythm can interfere with cortisol and melatonin production.

In the long-term, disruptions in circadian rhythm can lead to insulin resistance and increased risk of metabolic dysfunction, as well as changes in hunger-satiety signaling due to the impact of circadian rhythm on leptin and ghrelin. These changes in blood glucose regulation and hunger-satiety cues can lead to overeating and other behaviors that may lead to weight gain and metabolic syndrome. Long-term changes in circadian rhythm may also affect the female menstrual cycle, leading to symptoms like cycle irregularity and longer menstrual cycles. 

Assessing Circadian Rhythm Disruptions

A functional medicine assessment of circadian rhythm disruptions may include several different avenues to get a better picture of circadian health. Functional labs can be used to track hormone levels, including melatonin and cortisol, to assess circadian rhythm patterns and identify any deficits in these two hormones that are so critical to regular sleep-wake timing. The Sleep and Stress Panel by Ayumetrix is a test that specifically tracks cortisol and melatonin over the course of 24 hours. Additionally, levels of other hormones, such as fasting insulin and glucose, leptin, and sex hormones can also be tested to assess for long-term impacts of circadian rhythm disruptions on other hormone pathways.  

Wearable technology can be used to track body temperature, one of the primary makers used to assess circadian rhythm. Some wearable devices can also track sleep stages and restfulness, which may be helpful to track optimal sleep windows and keep track of any patterns with sleep disruptions. Devices such as continuous glucose monitors can help identify irregularities in blood glucose that may be contributing to further disruption of the sleep-wake cycle.

Last, patients may be asked to keep sleep diaries so that, alongside their practitioner, patterns may be identified in how diet, lifestyle, medications, or other factors may be negatively impacting circadian rhythm health and affecting their sleep quality.  

It’s important to consider both clinical data (such as lab results and data from wearable technology) as well as lifestyle factors for each patient when assessing circadian rhythm disruptions. Functional medicine practitioners are uniquely positioned to help patients optimize their circadian health through a holistic approach that considers the individual in creating personalized treatment plans.

Functional Medicine Strategies for Restoring Circadian Rhythms

Functional medicine practitioners can help restore and regulate the circadian rhythm through personalized diet and lifestyle recommendations. First, prioritizing sleep hygiene is a foundational piece of regulating circadian rhythms. Having a consistent bedtime and wake up time, sleeping in a dark and cool room, and minimizing artificial light in the bedroom are all important components of optimal sleep hygiene.  

Managing light exposure is also helpful for regulating circadian rhythms. Getting natural sunlight exposure within 30 minutes of waking or of sunrise also sends important regulatory signals to the SCN that helps to support a healthy circadian rhythm. Minimizing blue light exposure, especially after dark, is also essential for optimal sleep and a healthy circadian rhythm, as blue light viewed after dark has been found to be disruptive to circadian rhythm regulation.  

Stress reduction strategies are another important tool for restoring circadian rhythms. While it’s true that disruptions in the circadian rhythm can increase sensitivity and reactivity to stress, the converse is also true: chronic stress can negatively impact circadian health due to excess cortisol and catecholamine production. Helping patients incorporate stress reduction techniques such as meditation, breathwork, and exercise can help regulate the stress response and alleviate the potentially negative impact of ongoing stress on circadian rhythms. 

Diet and supplement recommendations may also be made to help restore circadian rhythm health, and are typically guided by testing and a comprehensive patient assessment. Meal timing recommendations can help regulate the circadian rhythm based on each patient’s lifestyle and job schedule, as timing of food intake is a potent regulator of circadian health - for example, eating late at night has been shown to disrupt circadian rhythm and interfere with sleep. Nutritional approaches like the Mediterranean diet may help with overall melatonin production and can also help keep blood sugar in check, two important areas to focus on when it comes to regulating circadian rhythms. Supplement recommendations may be made based on functional lab testing and patient assessment, and may include supplements to help regulate cortisol, such as adaptogens, as well as supplements to support sleep, including melatonin or L-theanine. Other root causes may be addressed using specific therapeutic diets and nutrition as well. 

Challenges and Future Directions

Diagnosing circadian rhythm disruptions can be challenging, and often requires a period of gathering information through sleep journals, patient assessments, wearable monitoring technology and lab testing to watch patterns in sleep and energy levels over time. Additionally, it can sometimes be challenging to treat these disruptions, particularly if an individual’s work schedule is a major contributing factor to their symptoms. Because disruptions in circadian rhythms can impact many different hormonal pathways, it can also be challenging to identify the common underlying factors contributing to hormonal imbalances in affected individuals. Treatment needs to address the hormonal symptoms, while also setting up a strong foundation for a healthy circadian rhythm that encompasses sleep hygiene, natural light exposure, and stress management.  

In the future, more research is likely to be directed at public health measures to support a healthy circadian rhythm, with special attention paid to shift workers.  Wearable technology can provide insight into the far-reaching impact of circadian health on stress hormones, sleep, and other aspects of health and wellbeing, and studying women in particular may bring to light the impact of circadian rhythm disruption on menstrual health and female hormone balance.  

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Circadian Rhythm and Hormone Health: Final Thoughts

Maintaining a healthy circadian rhythm is an important component of optimal hormone health, as circadian rhythms have far-reaching impacts on levels of cortisol, melatonin, insulin, estrogen, leptin, and other hormones.  While it can be tempting to “spot treat” hormone imbalance symptoms with supplements, including foundational lifestyle changes to support a healthy circadian rhythm can make a massive impact on patients’ overall hormonal wellbeing, and can set patients up for success in the long run when it comes to their energy, sleep, and hormone health.