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Cortisol: What It Is, What It Does

Updated: Oct 3, 2022

Cortisol is a hormone that plays an important role in your body. It's secreted by the adrenal glands, which sit above each kidney. Cortisol levels rise and fall throughout the day as your body responds to stressors such as physical activity, illness or injury, and temperature changes.

It's your body's main stress hormone.

Cortisol is a hormone that's secreted by the adrenal glands. It's released in response to stress, including physical and emotional stressors like exercise and psychological factors like anxiety.

When cortisol levels are high, it helps us deal with stress by increasing blood sugar, blood pressure, and blood flow to muscles. This gives us more energy so we can deal with the situation at hand — for example, if you're running away from an attacker who is about to attack you with some sort of sharp object.

Cortisol affects how much glucose (sugar) is in your blood.

Cortisol is a hormone that helps to regulate blood glucose levels. It does this by increasing the amount of sugar (glucose) in the blood by:

  • Increasing glycogen breakdown in your liver and muscles

  • Increasing gluconeogenesis (the creation of new glucose) in your liver, especially when you have low blood sugar levels

Decreasing insulin sensitivity, means your body needs more insulin to lower blood sugar levels.

Cortisol levels rise and fall throughout the day.

Cortisol levels rise and fall throughout the day, peaking in the morning and reaching their lowest point at night. Most people will have the highest levels of cortisol in the morning after waking up, although some people may experience a spike when they get stressed or experience a stressful event.

Cortisol levels can also be affected by diet, exercise, sleep deprivation, and psychological stress. For example:

  • If you're not getting enough sleep one night, your body might release more cortisol to help keep you awake.

  • If you don't eat breakfast every day (or any food at all), your body will start producing more cortisol to help keep itself alive for longer periods of time since it doesn't have enough energy coming from food sources like proteins or carbohydrates provided by eating regularly scheduled meals throughout each day's schedule (i.e., breakfast).

Cortisol levels are usually highest in the morning and lowest at night.

Cortisol levels are usually highest in the morning and lowest at night. This is because cortisol is produced in response to stress, and your body tends to be less stressed during sleep than it is while you're awake.

The hormone can also affect your weight and appetite, so if you've noticed that you're more likely to eat unhealthy foods when stressed, this may be why: Cortisol has been found to increase cravings for high-calorie foods (like fast food).

High cortisol levels can lead to weight gain and obesity.

One of the ways cortisol can lead to weight gain is by stimulating your appetite, causing you to eat more. In addition, high levels of cortisol can cause insulin resistance and high blood sugar levels. This leads to a condition called “insulin resistance syndrome” (IRS). IRS causes you to burn muscle instead of fat for energy, which can result in weight gain.

Your body has many ways of keeping your cortisol levels in check.

Once CRH reaches the pituitary gland, it stimulates the secretion of adrenocorticotropic hormone (ACTH). ACTH then travels to the adrenal glands, where it triggers a cascade of biochemical reactions that results in cortisol production.

Cortisol is released into your bloodstream at a slow but steady rate throughout the day. However, when you experience stress or trauma—whether mental or physical—your body releases large amounts of cortisol into your bloodstream all at once. This can happen in response to any number of events: a car accident; an argument with someone who's important to you; or watching news coverage about current affairs. The body adapts quickly enough so that when these events are over and done with, cortisol levels return to normal within 24 hours or less (unless they're part of chronic ongoing stress).

The adrenal glands make cortisol, aldosterone, and DHEA.

You might have heard of cortisol before. It's a hormone that's produced by your adrenal glands, small glands located above your kidneys. They're part of the endocrine system, which means they release hormones into the bloodstream to regulate various functions in your body.

Adrenal glands also produce two other hormones: aldosterone and DHEA (dehydroepiandrosterone). These are less well known than cortisol, but they help manage heart rate and blood pressure, store energy for use later on in life (as fat), stimulate growth during childhood and puberty, affect cholesterol levels—and much more.

How much cortisol does your body make?

The amount of cortisol in your body changes throughout the day. When you're not stressed, you have low levels of it. But when you are stressed, your body releases more cortisol to help deal with the situation (this is called "fight or flight").

Cortisol levels rise and fall throughout the day: they're highest in the morning and lowest at night. This means that how much cortisol is in your blood can give doctors information about how well your body is coping with stressors. If a doctor finds that there's too much cortisol in your blood at certain times during the day, there might be something wrong with how well-regulated your stress response system is—such as depression or PTSD—and therefore advise treatment options like medication therapy or behavioral therapy to help regulate this system.

It's important to keep your cortisol levels balanced for optimal health.

The body produces cortisol in response to stress. Cortisol is a hormone that helps regulate blood pressure, as well as metabolism, and digestion. When you're stressed, your body releases cortisol, which functions as an "alarm hormone" to help you cope with the negative event that has occurred.

However, if your cortisol levels are consistently high throughout the day—even when there isn't an obvious stressor present—it can signal an issue with your health. This happens because cortisol doesn't just affect how much glucose (sugar) is in your blood; it also affects how much fat is stored in your body by regulating which processes burn off excess energy (and which ones save it for later).

If you're interested in keeping track of exactly how much cortisol is being released into your system every day, there are several ways this can be done:

-A blood test can measure cortisol levels in your body. This is a good option if you're trying to determine if there is an underlying cause for high cortisol levels, such as an adrenal gland disorder or pituitary gland tumor.

-You can also have a saliva test to measure how much cortisol is in your system at any given time during the day. This method allows you to see how normal fluctuations in hormone levels affect energy output and metabolism over time, which can help identify patterns that indicate when you're most likely to experience stress (and, therefore, when it's best not to eat).


Cortisol is a hormone that affects how much glucose (sugar) is in your blood. It's also known as the "stress hormone," because it helps you deal with stressful situations. Cortisol levels rise and fall throughout the day, with highest levels in the morning and lowest at night. Your body has many ways of keeping your cortisol levels in check, including making more when needed or reducing production if they get too high. The adrenal glands make cortisol, which can be measured by drawing blood samples at different times of day to see what level of this hormone is being produced by your body's system at those moments.

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