What is cortisol?
Cortisol (also called hydrocortisone) is a steroid hormone produced in the adrenal cortex. It then enters the bloodstream. In the liver, the hormone is broken down and finally excreted through the kidneys in the urine.
How is cortisol produced?
The body controls cortisol production with the help of a sensitive regulatory circuit of various hormones. At the top is the corticotropin-releasing hormone CRH from the hypothalamus (part of the diencephalon). This is released in spurts and promotes the formation and release of a hormone from the pituitary gland – ACTH (short for adrenocorticotropic hormone).
ACTH, in turn, stimulates the formation and release of cortisol in the cortex of the adrenal gland. Under the influence of ACTH, the concentration of cortisol in the blood increases after only a few minutes.
However, our body also has a feedback mechanism built into the regulatory circuit: The released cortisol inhibits the release of CRH and ACTH, so that it does not lead to an ever-ongoing production and a cortisol surplus.
What are the functions of cortisol?
In summary, cortisol has the following effects:
- It activates or inhibits the transcription of various genes, i.e. in a sense the reading of the genetic information stored in the genes.
- As an antagonist to insulin, cortisol raises blood glucose levels.
- It promotes the breakdown of the body’s protein stores.
- It supports the dissolution of fat stores, among other things by increasing the effect of adrenaline.
- It increases the beating power of the heart muscle, blood pressure and respiratory rate.
- It prevents inadequate reactions of the immune system and inhibits inflammation.
- It inhibits the longitudinal growth of bones.
- In the central nervous system, cortisol increases attention and information processing, improves memory, and stimulates appetite.
In addition, cortisol is important for the development of the embryo, more specifically for the development of the lungs, kidney and heart, and the formation of the immune system.
When do you determine the cortisol level?
Cortisol level is especially important in the diagnosis and control of diseases of the adrenal gland such as:
- Cushing’s disease (disorder of the pituitary gland)
- Adenoma of the adrenal cortex (benign growth)
- malignant tumor of the adrenal cortex
- ACTH-producing tumor (for example, small-cell bronchial carcinoma)
- functional weakness of the adrenal cortex (Addison’s disease)
The doctor can measure cortisol in blood as well as in urine and saliva.
Cortisol: Function tests
To check the function of the hormonal regulatory circuit around cortisol, the doctor uses a series of functional tests. In these, he stimulates or inhibits individual steps of the regulatory circuit and observes the body’s response. Examples of such functional tests:
In the CRH test, the physician administers the hormone CRH to the patient. In the healthy person, there is an increase in the “follow-up hormones” ACTH and cortisol.
In the ACTH test, ACTH is administered, which normally causes cortisol levels to rise. In the case of a disorder of the adrenal cortex, this rise in cortisol is absent or significantly reduced.
In the metopirone test, the physician gives the patient metopirone – a substance that inhibits the enzyme 11-beta-hydroxylase. This ensures the conversion of deoxycortisol into cortisol. The enzyme blockade causes cortisol levels to drop, which in healthy individuals triggers a rise in ACTH. The body thus wants to increase cortisol production, but this only leads to an increase in deoxycortisol due to the enzyme inhibition. If this increase does not occur, there may be an impaired ACTH release or an enzyme defect in steroid hormone synthesis.
Cortisol levels: Table with normal values
Cortisol levels fluctuate significantly throughout the day due to the episodic CRH release. Therefore, when the blood sample is taken from the patient plays an important role. For blood sampling at 8 a.m., the following normal values apply depending on the age group:
|
Age |
Cortisol standard values (blood) |
|
until 1 week |
17 – 550 nmol/l* |
|
2 weeks to 12 months |
66 – 630 nmol/l |
|
1 to 15 years |
69 – 630 nmol/l |
|
16 to 18 years |
66 – 800 nmol/l |
|
from 19 years |
119 – 618 nmol/l |
* Conversion to micrograms per deciliter: nmol/l x 0.0363 = µg/dl
Cortisol level is highest in the morning. As the day progresses, it decreases. Thus, when blood is drawn at 11 p.m., the cortisol level is usually below 138 nmol/l for all age groups.
Cortisol in urine
Cortisol can also be determined in 24-hour urine collection. The normal range for all age groups here is 79 to 590 nmol/24 h.
When is cortisol decreased?
A chronically low cortisol concentration is called hypocortisolism. Typical symptoms include decreased performance, weakness, nausea, and low blood pressure. The cause is a functional disorder of the adrenal cortex (adrenal insufficiency). Doctors distinguish between primary, secondary and tertiary forms of insufficiency, depending on the location of the disorder:
Primary hypocortisolismu
- Bleeding
- Tumors of the adrenal cortex (including metastases from tumors in other parts of the body)
- Infections such as tuberculosis
- Removal of the adrenal gland during surgery
- Taking certain medications (for example, the sleep-inducing anesthetic etomidate)
In addition to the general symptoms of low cortisol, unfortunately, patients with Addison’s disease suffer from hypoglycemia, loss of fluid and sodium through the kidneys, hyperacidity (acidosis), and severe pigmentation of the skin.
Secondary and tertiary hypocortisolism
If the damage is in the brain, i.e. in the pituitary gland or in the thalamus, the physician speaks of secondary or tertiary hypocortisolism. The most common cause is the abrupt discontinuation of long-term cortisol therapy. Sometimes, however, trauma or large benign growths (adenomas) are behind it.
When is cortisol elevated?
If the cortisol is too high, the doctor speaks of hypercortisolism or Cushing’s syndrome. The majority of Cushing’s syndromes are due to the administration of glucocorticoids such as in autoimmune diseases. Other causes of elevated cortisol levels are cortisol-producing tumors of the adrenal cortex or ACTH-producing tumors. The latter can arise in the pituitary gland as well as in other regions of the body.
High cortisol level: Consequences
A permanently elevated cortisol level leads, among other things, to:
- Osteoporosis
- Atrophy of the musculature
- Fat storage on the trunk of the body (trunk obesity with bull neck and round full moon face)
- High blood pressure
- Weakness of connective tissue
- thin skin
- delayed wound healing
- stomach ulcers
- diabetic metabolism
- edema (water retention in the tissue)
- depressed mood
If the present disease simultaneously leads to increased ACTH levels, the synthesis of male sex hormones is increased in addition to cortisol production. In affected women, the menstrual cycle is disrupted. In addition, a male pattern of hair (like beard growth) may develop.
What to do if cortisol levels change?
Due to the individual fluctuations in hormone levels, a single cortisol value has little significance. Better information is provided by repeated measurements or the special stimulation tests mentioned above.
If the cortisol value is too high because a hormone-producing tumor is present, this is surgically removed and/or treated with medication. In the second case, drugs are administered that inhibit the synthesis of cortisol.
In the case of hypocortisolism, on the other hand, the physician prescribes hormone replacement therapy with drugs containing precursors of cortisol.
