What is Plasma Cortisol?

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  • Written By: Mary McMahon
  • Edited By: Kristen Osborne
  • Last Modified Date: 08 October 2019
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Plasma cortisol is a laboratory test used to determine levels of the hormone cortisol in the blood. Cortisol levels can provide important information about a patient's health and may be used in the diagnosis and management of a number of conditions, most related to the adrenal gland, the site where cortisol is produced. In a plasma cortisol test, blood is drawn from a patient and analyzed in the lab. Several samples may be requested.

In healthy individuals, the adrenal gland makes cortisol to aid with a number of metabolic functions. Levels of this hormone in the body fluctuate over the course of the day, with afternoon levels typically being about half those in the morning. If the levels are unusually high or low, it can be an indicator that a patient has a condition like Cushing's disease, Addison's disease, or adrenal insufficiency. High levels can also be an indicator of stress, as cortisol tends to rise in response to stress.

Before a plasma cortisol test, patients may be advised to eat and exercise normally, fasting for around 12 hours before the blood sample is taken. If possible, patients will need to stop taking medications that might influence cortisol levels for two days before the test. If doing this would put the patient's health at risk because those medications are needed for survival, the patient can continue using them and a note will be made so laboratory technicians are aware of the potential for skewed results.


A common procedure involves drawing a sample in the morning and another in the evening. The plasma cortisol levels will be compared both to determine if they are within normal range and to see if they fall over the course of the day, as expected. This is an outpatient procedure, with patients leaving after the blood draw. Depending on the results, additional tests may be requested or a doctor may discuss options for management of abnormal plasma cortisol levels.

When this test is recommended, patients may want to ask their doctors why and get more information about how plasma cortisol is relevant to their diagnosis and treatment. This test is applied in a number of different ways and being aware of what the doctor is looking for can help patients prepare more adequately. It's also important to go over any symptoms currently being experienced, as they can provide important clues to the nature of a patient's condition.


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Post 3

@Mor - Not just wrinkles. High cortisol levels can lead to other bad things in old age, since it can stop the bones from developing properly, eventually leading to, or at least aggravating osteoporosis.

It can also lower fertility levels (which might be one reason why people who "stop trying" seem to get pregnant more easily than others who are stressed over it).

It can also suppress the immune system.

And, of course, what many people are worried about right now, is that it is suspected cortisol levels and weight gain might be related. It seems to affect blood sugar levels, at least, and possibly the storage of body fat. I've even heard some suggest it affects where fat is stored, and that high levels of cortisol might lead to fat being stored on the middle, which is the worst place for it.

At any rate, it's definitely worth trying to reduce stress as much as possible.

Post 2

Cortisol is one of those hormones that you hear a lot about because it is involved in stress. Even more than adrenaline, it gets continuously released if someone is being subjected to low levels of stress.

It also seems to affect, or perhaps be affected by depression, and some other afflictions, like Autism.

It seems to affect all kinds of systems, particularly as people get older. So, for example they have noticed that increased levels of cortisol hormone leads to greater loss of collagen in the skin, which is one of the causes of wrinkles.

So, yes, being too stressed can lead to wrinkles forming, it's not just something your mother said in order to get you to be quiet.

Post 1

I remember they had a patient on House who had abnormally low cortisol levels.

It was on one of the first episodes after House had lost confidence, and he was trying to diagnose a patient who was in a wheelchair, completely unresponsive to the people around him.

House realized after a while that the man must have Addison's disease, but he had already tried so many crazy stunts in diagnosing the patient, that the hospital refused to let him treat the patient, even though the treatment was only a simple injection of cortisol (or hydrocortisone anyway, which is the medication for increasing cortisol levels I think).

Of course, one of the other doctors managed to slip the man the medication he needed and he made a miraculous recovery. From what I can tell, they exaggerated the disease and the effects of the treatment for the drama, but it was still quite a good episode.

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