Melatonin: Hormones and Metabolism

Written by: Dr. Justine Luchini



Time to read 7 min

Melatonin is a hormone naturally produced by the pineal gland in the brain, and it plays a crucial role in regulating the sleep-wake cycle. It helps signal the body that it's time to sleep and promotes drowsiness. Many people turn to melatonin supplements as a sleep aid, but it's important to understand that melatonin may not be suitable for regular or long-term use due to its effects on other hormones and your metabolism.


So, to be clear, I think there is a role for melatonin use in short-term sleep timing and rhythm challenges. I also thing that in older populations and certain disease groups – there is interesting literature on how taking melatonin can be helpful (Alzheimers, certain cancers, etc). 

Even in those cases though, most people are probably taking way too much. Doses in the 0.3mg -1.5mg range are a reasonable amount. But most people take supraphysiological doses in the 5mg -10mg range. 

For people who are generally healthy and not menopausal – the concern is that melatonin has impacts on sex hormones and metabolic hormones. There is some research to suggest that there are suppressive effects on these systems. 

Consider that seasonally we have higher circulating melatonin in the winter (when the days are shorter and we have greater exposure to darkness) AND this goes along with us being metabolically slower. Many species that don’t mate in the winter have their sex hormones suppressed by very high circulating melatonin levels. There are some preliminary human, primate, and other animal studies that point to this. 

Basically – the long term positive effects of taking melatonin for sleep may be virtually zero and the potential unwanted effects on other hormones and our metabolism likely outweigh the sleep benefits in healthy populations.

Hormonal Disruption

Melatonin interacts with various hormones in the body, including cortisol, the stress hormone, and reproductive hormones such as estrogen and testosterone. Prolonged or excessive use of melatonin supplements can disrupt the delicate balance of these hormones, leading to potential side effects and imbalances.


For instance, studies show that melatonin may act as an inhibitor to (meaning interferes with), the human chorionic gonadotropin (hCG) pathway. This can have effects on androgen production (hormones like DHEA and testosterone). It can also interact with the local corticotropin-releasing hormone (CRH) system. The CRH system is involved in how we respond to stress and how our bodies use energy.


These hormone interactions should raise some flags of potential concern for the long-term use of melatonin - especially in people trying to maintain their fertility and in children. 

Metabolic Effects

Melatonin can also impact metabolism, specifically through glucose regulation - or how we use and produce energy from sugar. 


Studies have suggested that melatonin supplementation may affect insulin sensitivity, glucose tolerance, and overall metabolic function.


For example, a study published in the journal Cell Metabolism, which used both mouse and human models, 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, or low blood sugar levels at night, when melatonin levels are high but energy demands are low.

Another study, published in the journal Clinical Endocrinology, focused on postmenopausal women. The researchers administered either 1 mg of melatonin or a placebo to the participants in the morning. After 45 minutes, they conducted glucose tolerance testing. The study found that those who received melatonin had reduced glucose tolerance and lower sensitivity to insulin. 

This means their bodies had more difficulty processing and controlling blood sugar levels compared to those who took the placebo.

In a separate study published in 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 is used 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.

These studies highlight that melatonin can influence our body's metabolism and ability to regulate blood sugar levels - and that the effects can spillover into the next day. 

However, it's important to remember that these effects can vary depending on the time of day and individual factors. The research provides valuable insights into the complex relationship between melatonin and metabolic health.


Tolerance and Dependance

Regular use of melatonin supplements can lead to a decrease in the effectiveness of the hormone over time.

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

This means that higher doses may be required to achieve the same sleep-inducing effects, leading to a potential cycle of dependence. Additionally, abruptly discontinuing melatonin after prolonged use may result in rebound insomnia or sleep disturbances.

Final Thoughts: Melatonin Is Complicated

It's clear that, while melatonin most often gets associated with the idea of “sleep”, it has many other roles to play. It is one of nature's most versatile biological signals.

There are many studies pointing to the benefits of melatonin. Which also has to do with the fact that it plays to many roles. 

We certainly do not want too little of it. With increased levels of stress and increased light exposure, especially at night time, there is also a case to be made that many people might have low levels of melatonin. 

As with all hormones, there is a ‘Golidlocks’ zone. We do not want to have too much or too little of this hormone. The best case being that we have good consistent bed time habits, manage the light in our environment, and support our body with the right nutrients to make the right amount of melatonin (at the right time) on its own. 

If you're someone who relies on melatonin to sleep, you might be thinking “uh oh" or “what now?” 

I've been there. 

Two things are true. 
1. If you've been taking melatonin for a long time, and you want to stop, tapering it off is going to be less jarring to your system. 

2. There are other ways to naturally support your rest and recovery at night. 

Our PM Recovery Collagen was made to be a healthy, melatonin-free alternative in a sleep supplement market flooded with products that all seemed to contain melatonin, CBD, and/or sedatives. 


Instead, we harnesses the power of glycine, L-theanine, GABA, and magnesium, in carefully researched amounts, to provide a comprehensive approach to improving sleep quality, optimizing overall health, and boosting recovery potential.

You can add it to your regular sleep routine with out worrying about dependancy, or negative effects on your hormones or metabolism. 


Sleep tight,

Dr J


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.




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