How Melatonin Affects Your Hormones and Metabolism

Melatonin supplements are a common sleep aid, but do the benefits outweigh the risks? Let’s take a look at what melatonin can mean for your hormones and metabolism. After reviewing the science, you’ll be better equipped to determine whether you want to use melatonin or a melatonin free sleep aid.

What Is Melatonin?

Melatonin is a hormone your brain’s pineal gland naturally produces. It plays a crucial role in regulating your sleep-wake cycle, signaling your body that it's time to sleep and promoting drowsiness. 

Although people commonly associate melatonin with sleep, it’s one of nature’s most versatile biological signals and plays a role in many other bodily functions. In fact, melatonin supplements may not be suitable for regular or long-term use due to melatonin’s effects on other hormones and your metabolism.

How Does Melatonin Affect Hormones?

Melatonin can affect other hormones in your body, such as your sex hormones and metabolic hormones. It may do this by influencing which hormones your pituitary gland releases and when. Some research suggests melatonin has suppressive effects on your reproductive and metabolic systems. For people who are generally healthy and not menopausal, this should be a concern.

Melatonin and your other hormones are all components in an intricate web of your bodily processes. When your endocrine system is healthy and regulating these levels just as it should, everything functions smoothly.

For example, did you know you have higher levels of circulating melatonin in the winter? When the days are shorter and you typically have greater exposure to darkness, your melatonin levels rise. This coincides with people being metabolically slower during this time of year.

Interestingly, many species that don’t mate in the winter have very high circulating melatonin levels that suppress their sex hormones. There are some preliminary human, primate, and other animal studies that point to melatonin’s suppressing effects on sex hormones. 

What Is Hormonal Disruption?

Hormonal disruption occurs when an external factor, such as the introduction of a chemical, interferes or even blocks the normal functions of your body’s endocrine system. Examples of hormone disruptors, also called endocrine disruptors, include pesticides, certain preservatives (such as parabens), and many compounds in plastics and resins (like Bisphenol A, or BPA).

By making it impossible for your endocrine system to function as it should, hormonal disruption can cause a number of health issues. Researchers have found links between endocrine disruptors and problems related to reproduction, child development, neurology, and other areas.

Does Melatonin Cause Hormonal Imbalance?

Prolonged or excessive use of melatonin supplements can disrupt the delicate balance of your hormones, leading to potential side effects and imbalances.

For example, melatonin can interact with cortisol (the stress hormone) and with the reproductive hormones estrogen and testosterone. It also interacts with the corticotropin-releasing hormone (CRH) system, which is involved in how your body uses energy and other processes. 

There are more ways melatonin can cause hormonal imbalances. Studies show that melatonin may act as an inhibitor to the pathway of human chorionic gonadotropin (hCG). This is a hormone that a pregnant woman’s placenta produces. HCG signals to other areas of the woman’s body that she is pregnant, and it triggers or supports many of the physiological changes that accompany a pregnancy (hCG is the hormone that most pregnancy tests are designed to detect in a woman’s urine).

Interference with the hCG pathway can also have effects on the production of androgens — the hormones that are mainly responsible for male characteristics, although androgens are present in both males and females. Examples of androgens include the hormones testosterone and DHEA. 

These hormone interactions understandably raise some red flags about the long-term use of melatonin for people who are trying to maintain their fertility, lean body mass and protect their children.

What Is a Melatonin Hormone Disruptor?

Don’t confuse melatonin’s potential to disrupt your hormones with the term “melatonin hormone disruptor,” as these refer to different things. While excessive melatonin use can interfere with your body’s hormones, a melatonin hormone disruptor refers to something that disrupts your body’s melatonin production. 

In other words, a melatonin hormone disruptor is any factor, chemical or otherwise, that can interfere with your body’s normal melatonin levels. Examples include caffeine, bright artificial light, advanced age, jet lag, and certain diseases.

Does Melatonin Affect Estrogen Levels?

Melatonin has potentially anti-estrogen effects, meaning it might reduce or block the production of estrogen, or it may interfere with estrogen’s ability to circulate effectively in your body. Some studies have shown that as melatonin levels increase, estrogen levels decline, and vice versa.

In the long term, melatonin interfering with estrogen levels can disrupt a woman’s menstrual cycle or lead to fertility complications.

The Effects of Melatonin on Metabolism

Melatonin can also impact your metabolism, specifically through glucose regulation, or how you use and produce energy from sugar. Studies have suggested that melatonin supplementation may affect insulin sensitivity, glucose tolerance, and overall metabolic function.

Study Example #1

For example, a study in the journal Cell Metabolism used both mouse and human models. It found that higher levels of melatonin can negatively affect the ability of beta cells to produce insulin. Beta cells are important for controlling blood sugar levels. 

The researchers also discovered that this effect is more prominent in individuals who have a specific gene variant in the melatonin receptor gene MTNR1B, which is associated with a higher risk of Type 2 diabetes. Interestingly, the study revealed that inhibiting insulin may have a protective effect against nocturnal hypoglycemia (low blood sugar levels at night), when melatonin levels are high but energy demands are low.

Study Example #2

A study in the journal Clinical Endocrinology focused on postmenopausal women. In the morning, the researchers administered either 1 mg of melatonin or a placebo to the participants. After 45 minutes, the researchers conducted glucose tolerance testing. The study found that those who received melatonin had reduced glucose tolerance and lower sensitivity to insulin. This means those participants’ bodies had more difficulty processing and controlling blood sugar levels compared to those who received the placebo.

Study Example #3

In a study from the journal Sleep, researchers investigated the effects of supplemental melatonin on glucose tolerance in healthy women. They primarily focused on two important measures: the incremental area under the curve (AUC), which describes the total rise in glucose over time and which experts use to diagnose impaired glucose tolerance, and the maximum concentration (Cmax) of plasma glucose. 

The study revealed that melatonin supplementation in the evening decreased insulin sensitivity, resulting in a 54% increase in glucose AUC and a 27% increase in glucose Cmax. In the morning, melatonin impaired glucose tolerance by reducing insulin release, leading to a remarkable 186% increase in glucose AUC and a 21% increase in glucose Cmax.

What the Studies Tell Us

These studies highlight that melatonin can influence your body’s metabolism and ability to regulate blood sugar levels, and that the effects can spill over into the next day. The research provides valuable insights into the complex relationship between melatonin and metabolic health. However, it’s important to remember that the effects can vary depending on the time of day and individual factors. 

Melatonin As a Sleep Aid: Good or Bad?

There is a role for melatonin use in short-term sleep timing and rhythm challenges as long as the dose is a reasonable amount — 0.3 mg to 1.5 mg. However, there are people who regularly take supraphysiological doses in the 5 mg to 10 mg range, which is inadvisable. “Supraphysiological” means an amount well above and beyond what your body can naturally produce or process.

There is interesting literature on how taking melatonin could be helpful for seniors and those in certain disease groups, such as those affected by Alzheimer’s or certain cancers (again, as long as the dosage is reasonable). But for the rest of the population, the potential unwanted effects of long-term use, including hormonal disruption or hormonal imbalance, likely outweigh the potential benefits.

The decision whether or not to use melatonin in your personal sleep stack is therefore a personal choice, one that you should research carefully and make in consultation with your healthcare specialist. 

Melatonin Tolerance and Melatonin Dependence

Does the regular use of melatonin supplements lead to a decrease in the hormone’s effectiveness over time? Studies are inconclusive. If a person requires gradually higher doses to achieve the same sleep-inducing effects, this would be called melatonin tolerance and could lead to a potential cycle of melatonin dependence. 

Alternatively, abruptly discontinuing melatonin after prolonged use may result in rebound insomnia or sleep disturbances.

Some studies have shown that the long-term positive effects of taking melatonin for sleep appear to be limited. They find that after 12 months, the sleep of participants isn't measurably different from that of people who are taking a placebo.

How to Stop Taking Melatonin

If you've taken the hormone as a sleep aid for a long time and you want to quit melatonin, there is a safe way to stop taking melatonin: Do it gradually. Tapering off will be less jarring to your system. Ideally, you will also keep good bedtime habits, manage the light in your environment, and support your body with nutrients so it can make the right amount of melatonin (at the right time) on its own.

Another way to naturally support your rest and recovery at night is to switch to a melatonin-free sleep supplement. Look for a product that doesn’t contain melatonin, CBD, or sedatives. Your best options will even offer additional benefits by incorporating ingredients like glycine (of which sleep expert Dr. Andrew Huberman is a proponent), L-theanine, GABA, and magnesium in carefully researched amounts. All of these support your body’s nightly recovery processes, including your muscle recovery.

Final Thoughts

By now it should be clear that while most people associate melatonin with sleep, it plays many other important roles in your body. And as with all hormones, there is a “Goldilocks” zone. You don’t want to have too much or too little, and you don’t want imbalances to last for extended periods of time. 

Fortunately, you have alternatives when it comes to the different types of sleep supplements — melatonin isn’t your only option. 

For example, maybe a magnesium powder or a collagen sleep aid would better help you meet your health goals. Whichever supplement you choose, you should be able to add it to your regular sleep routine without worrying about dependency or negative effects on your hormones or metabolism.

Remember, at the end of the day (pun intended), your needs are unique. Choose the product that will provide you with the most comprehensive approach to improving your own individual sleep quality, optimizing your overall health, and boosting your recovery potential.

Sleep tight,

Dr. Justine Luchini

This blog is not intended to be used as medical advice. Any decision to supplement should be done in consultation with a healthcare professional who understands your unique health circumstances and needs.

References

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