How does cortisol affect metabolic health?
Too much of this stress hormone may increase the risk of Type 2 diabetes and other conditions. But you can take action to keep cortisol in check.
Cortisol is best known as a stress hormone, but it plays a much bigger role in our bodies. At the right levels, it manages our sleep-wake cycle, helps combat inflammation, contributes to healthy metabolism, and assists in regulating blood glucose.
The tricky thing is that, while we need cortisol, both too little and too much of the hormone can negatively impact health. If your cortisol levels are too low, you may have adrenal insufficiency and experience weight loss, extreme fatigue, and hypoglycemia. And if your cortisol is too high, it can lead to Cushing syndrome, which is marked by symptoms such as weight gain around your midsection and in your face, wide reddish-purple stretch marks, and easy bruising.
Chronic high cortisol can also keep blood glucose elevated, increasing the risk of insulin resistance, Type 2 diabetes, and metabolic syndrome. Don’t stress, though. Here’s everything you need to know about cortisol, how to know where your levels are, and what to do if you could benefit from lowering your cortisol.
What is cortisol and what does it do?
Cortisol is part of a group of steroid hormones known as glucocorticoids, which are made in the outer part, or cortex, of your adrenal glands. Once created, cortisol is released into your blood, which shuttles it throughout your body.
Almost every cell that you have contains receptors for cortisol, so the hormone affects pretty much all of your organs. It has many different actions, depending on what type of cell it’s acting on. It plays a role in:
- Regulating the stress response (i.e. fight or flight). When you encounter a stressor, the hypothalamus sets off a series of hormonal shifts, including an increase in cortisol. This keeps your body primed to react to threats.
- Controlling blood sugar levels. Cortisol counterbalances the effects of insulin. It elevates your blood sugar by releasing stored glucose into your bloodstream.
- Keeping metabolism humming. Cortisol helps control how your body uses fats, proteins, and carbohydrates for energy.
- Managing salt and water balance. Cortisol increases the rate of blood that flows through your kidneys. This impacts the amount of salt and water released into your body.
- Regulating blood pressure. While the mechanism isn’t clear, it’s known that high cortisol levels raise blood pressure, while low cortisol levels lower blood pressure.
- Governing the sleep-wake cycle. Your cortisol levels dip at night before bedtime and rise in the morning, helping you to wake up.
Your body controls cortisol by a very precise mechanism known as the hypothalamic-pituitary-adrenal axis. Here’s how it works:
- When blood cortisol levels drop, your hypothalamus—the part of the brain that produces hormones that control essential functions such as body temperature, heart rate, and feelings of hunger and thirst—releases corticotropin-releasing hormone. This signals your pituitary gland to release another hormone (adrenocorticotropic hormone) into your bloodstream.
- The rise of adrenocorticotropic hormones stimulates the release of cortisol.
- As your cortisol levels rise, they block the release of both corticotropin-releasing hormone and adrenocorticotropic hormone. This in turn causes cortisol to drop, so that it doesn’t get too high.
How does cortisol affect metabolic health?
In a healthy person, cortisol triggers the release of stored glucose from the liver. In turn, blood glucose levels rise, giving us quick-acting energy. But when cortisol levels remain elevated (as can happen with chronic stress), things go awry.
To start, more cortisol means more glucose is released into the blood. Over time, this can lead to insulin resistance and dyslipidemia (abnormal cholesterol).
Long-term high cortisol levels also increase inflammation, which is associated with diseases such as stroke, chronic respiratory diseases, heart disorders, cancer, obesity, and diabetes. Chronically high cortisol may also be associated with metabolic syndrome, as it raises blood pressure, cholesterol, and blood sugar levels—three of the five risk factors for the condition.
Then there’s the fact that chronic high cortisol may lead to weight changes. This happens for a few reasons:
- Excess cortisol can drive the accumulation of visceral fat—the deep belly fat surrounding organs that is linked with cardiovascular and other risks—through several mechanisms, including increased insulin resistance and hormone imbalances.
- Cortisol also triggers fat and carbohydrate metabolism, which in turn stimulates your appetite and may lead you to overeat.
- Too much cortisol over the long term also causes your body to produce less testosterone. This can both cause a decrease in muscle mass, induce insulin resistance in muscle, and drive visceral fat gain.
Signs your cortisol may be out of whack
Only testing can tell you for certain what your cortisol levels are. However, if you have the following symptoms, your body may be trying to tell you something is off.
High cortisol may cause:
- Weight gain
- High blood glucose
- High blood pressure
- Purple stretch marks on the stomach
- Fatty deposits between the shoulder blades
- Weakness in the thighs and upper arms
- Bone fractures
- Excessive hair growth
- Low sex drive
- Irregular periods
- Anxiety
- Depression
Low levels of cortisol may lead to:
- Weight loss
- Fatigue
- Low blood pressure
- Appetite loss
- Dizziness, especially when you stand
- Muscle weakness
- Mood changes
- Darkening of regions of your skin
Over time, without treatment low levels of cortisol can be life-threatening.
Why test cortisol?
If you have any of the above mentioned symptoms, you may want to test your cortisol. Depending on your symptoms, your doctor may want to test you for either Cushing’s syndrome (where your body makes too much cortisol) or Addison’s disease (where your body makes too little of this hormone). These conditions can cause serious health complications if left untreated.
There are several different ways to get tested:
- Blood tests: Your doctor or another medical professional will draw blood from your arm. This is usually done twice during the day—once in the morning, when cortisol levels are at their highest, and once around 4 p.m., when levels are typically lower.
- Urine tests: You collect all your urine during a 24-hour period. (You’ll receive a special container with instructions on how to collect and store the urine sample.) You then send it back to your doctor’s office or a laboratory.
- Saliva tests: These are done at home with a test kit. Most companies recommend that you collect your saliva at night before you go to bed when cortisol levels are lower. Follow the instructions that come with your kit, and don’t eat, drink, or brush or floss your teeth for a half hour before the test.
If you want to try an at-home test, choose one from a company that uses CLIA-certified labs. This means that they meet government guidelines for quality standards. This will help ensure that the results are accurate. Some options include, ZRT Labs, Lets Get Checked, Rx Home Test, My Lab Box, and Rootine.
What are optimal cortisol levels?
Cortisol peaks in the morning and declines throughout the day, so optimal levels depend on when you test. Normal ranges can also vary from lab to lab, time to time, and person to person.
For most tests that measure cortisol levels in blood, normal ranges are:
- 8 a.m.: 5 to 23 micrograms per deciliter (mcg/dL)
- Around 4 p.m.: 3 to 13 mcg/dL
How can you improve your cortisol?
If testing shows that your cortisol levels are too high or too low, see your healthcare provider to rule out a medical condition, such as Cushing’s syndrome or Addison’s disease. But if your cortisol levels are borderline, certain lifestyle changes that support metabolic health may also reduce high cortisol[HL1] . This may include:
Meditation. Research shows an association between increased mindfulness and decreased levels
of cortisol. For these studies, mindfulness can include multiple types of meditation but all show some effect and to help to lower levels of stress hormones.
Improve your sleep. Too little sleep and poor sleep may both increase cortisol levels. In fact, just one night of bad sleep is associated with changes in both insulin and cortisol. If zzzs are hard to come by, start with small changes: set a regular sleep schedule, keep your bedroom quiet and dark with things like a white noise machine and blackout shades, and avoid looking at screens as bedtime approaches.
Stay active—but don’t overdo it. Exercise can lower cortisol, since it helps to relax you and lower stress levels. But it’s important not to overtrain. Some research suggests that endurance athletes, for example, have higher cortisol levels, probably because their bodies are under physical stress for long amounts of time. Focus on regular moderate exercise like brisk walking and bodyweight strength training three to four times per week.
Spend time outside. A 2019 review published in the International Journal of Biometeorology found that the practice of forest bathing—a Japanese practice in which you spend time in nature engaging your senses—has short-term positive effects on cortisol. Another study found that when 36 city dwellers spent at least 10 minutes in nature three times a week for eight weeks, their levels of cortisol temporarily dropped.
Watch a funny movie. Spontaneous laughter lowers cortisol levels by about a third, according to a 2023 review of eight studies published in the journal PLOS One. Laughter can also stimulate circulation and aid muscle relaxation, both of which can help reduce some of the physical symptoms of stress.
Find caring companions. One study found that having friends one could talk to about marriage challenges reduced their physical stress response. The same holds true for furry friends: Just 10 minutes of petting a cat or a dog has been shown to temporarily lower cortisol levels.
Conclusion
Cortisol serves an important function in metabolic physiology under normal conditions and in the stress response. The cortisol peak after waking is important for synchronizing metabolic control to enhanced mental alertness and physical activity. Persistently high cortisol later in the day could be a sign of a problem and may require additional tests by your doctor. Although not everyone needs to optimize cortisol, testing is simple and inexpensive for those interested in learning more.
