If there is a suspicion of dysfunction of the adrenal cortex, endocrinologists prescribe a small dexamethasone test to patients. This study with high accuracy allows you to establish the cause of the increase in cortisol levels in the blood. Such a test plays an important role in the diagnosis of hormonal disorders in women and men. How is the test done? And how to interpret the analysis data? We will consider these issues in the article.
What is hypercorticism
An increased concentration of cortisol in the blood is called hypercorticism or Itsenko-Cushing's syndrome. This substance is produced by the adrenal cortex and belongs to glucocorticoid hormones. Elevated cortisol levels lead to the following disorders:
- overweight;
- increased body hair in women;
- menstrual disorders;
- the appearance of striae (stretch marks) on the skin;
- persistent increase in blood pressure;
- increased fragility of bones;
- decreased immunity;
- infertility.
Hypercorticism is a rather dangerous condition that can indicate serious disorders of the adrenal gland or pituitary gland.
Causes of Hypercorticism
All causes of increased levels of cortisol can be divided into endogenous and exogenous. In the first case, there is a constant hyperfunction of the adrenal cortex. The main cause of endogenous hypercorticism is Itsenko-Cushing's disease - pituitary adenoma. With this pathology, the production of adrenocorticotropic hormone increases, which stimulates the function of the adrenal cortex.
Other endogenous causes of hypercorticism are tumors and hyperplasia of the adrenal cortex. In this case, gland hyperfunction is provoked by pathological changes in its structure.
The exogenous causes of increased levels of cortisol include, above all, prolonged use of corticosteroids. Such drugs are prescribed for inflammatory processes, allergies and autoimmune pathologies. The constant intake of synthetic analogues of steroid hormones in the body can trigger an increase in the concentration of cortisol.
Other exogenous causes of hypercorticism can be distinguished:
- alcohol abuse
- taking hormonal contraceptives;
- obesity;
- diabetes;
- hepatitis;
- pregnancy.
In the above cases, an increase in cortisol is not associated with impaired pituitary and adrenal gland function. It is temporary. Signs of hypercorticism disappear after eliminating its cause.
What analysis shows
Small dexamethasone test is used for the differential diagnosis of endogenous and exogenous hypercorticism. The drug "Dexamethasone" is a synthetic analogue of glucocorticoids. A large single dose of this medication causes a decrease in the natural production of cortisol.
If hypercorticism is provoked by exogenous causes, then after using this drug, the patient's blood concentration of cortisol decreases sharply. In case of dysfunction of the pituitary gland and adrenal glands, the level of this hormone weakly responds to the intake of Dexamethasone.
Thus, the analysis makes it possible to distinguish true hypercorticism in diseases of the pituitary and adrenal glands from a temporary and functional increase in the concentration of cortisol.
Large and small sample: differences
When diagnosing endocrinological pathologies, doctors use a large and small dexamethasone test. Consider the differences between these two types of analyzes.
First, doctors determine the concentration of cortisol in the blood before taking corticosteroids. Then, with a small sample, the patient consumes from 2 to 8 tablets of "Dexamethasone" for 2 days, and with a large sample - from 16 to 32 tablets. Thus, these two types of test differ in the amount of drug taken. After using a corticosteroid, blood is taken for analysis again and the level of cortisol is determined.
A small dexamethasone test helps to distinguish an exogenous increase in cortisol from endogenous hypercorticism. A large sample is used for more detailed diagnostics. This analysis allows us to differentiate the adrenal and pituitary forms of hypercorticism.
If during a large test there is a sharp decrease in the concentration of cortisol after taking Dexamethasone, then this indicates the pituitary origin of the pathology (Itsenko-Cushing's disease). If hypercorticism is caused by hyperplasia or a tumor of the adrenal cortex, then the level of the hormone decreases very slightly.
Indications
A small dexamethasone test is prescribed in the presence of the following symptoms:
- Disproportionate obesity. With hypercorticism, fat is deposited mainly in the face, abdomen and back. The limbs may look thin.
- Hirsutism. In women with hypercorticism, hair growth is observed in the chin area, above the upper lip and on the chest.
- Menstrual disorders and infertility. Impaired cortisol production leads to impaired reproductive function.
- High blood pressure. Enhanced secretion of corticosteroid hormones causes persistent hypertension.
- Stretch marks (striae) on the skin of the abdomen. Dysfunction of the adrenal cortex causes atrophic changes in the skin.
- High blood glucose. Hypercorticism can lead to the development of diabetes.
- Decreased immunity. Excessive secretion of corticoid hormones suppresses the body's defenses. This leads to frequent colds and skin infections.
The analysis is indicated if the patient has several of the above symptoms.
Training
Conducting a small dexamethasone sample does not require special preparation. The first portion of blood is taken in the morning on an empty stomach. On the eve of the study, it is necessary to exclude physical and emotional overload, since stress affects the level of cortisol. It is also necessary to stop the use of analgesics, hormonal contraceptives, anticonvulsants and sleeping pills a day before the analysis.
The test is carried out in two ways: classic and shortened. Let's consider them in more detail.
Classic method
In the classic version of the sample, venous blood is taken in the morning at 8.00. The biomaterial measures the level of cortisol. Then, within 2 days, the patient takes 1 tablet (0.5 mg) of the drug with dexamethasone every 6 hours. On the third day at 8.00, blood is taken again and the concentration of the hormone of the adrenal glands is again determined.
The accuracy of a small dexamethasone sample in the classical version approaches 100%.
Shortened version
In the morning at 8.00 they take blood from a vein to determine the concentration of cortisol. 15 hours after the delivery of the biomaterial (at 23 hours), the patient takes a single dose of 2 tablets (0.5 mg) of the drug. On the second day at 8.00 it is necessary to pass a second test for hormone levels.
The accuracy of this research method is about 95%.
What do the test results mean?
Consider the interpretation of a small dexamethasone sample. Before taking the drug, the level of cortisol in adults normally ranges from 138 to 635 nmol / L. For children, reference values from 90 to 580 nmol / L are allowed.
During pregnancy, the level of this hormone increases by 3.5-4 times. This is not considered a pathology and is assessed as a variant of the norm.
If the decoding indicates a positive result, then this means that after taking Dexamethasone, the level of cortisol is less than 50 nmol / L. Such indicators are observed in healthy people, as well as in patients with exogenous hypercorticism.
If a negative result is noted in the decoding of a small dexamethasone sample, then this indicates that after taking the tablets, the concentration of cortisol is more than 140 nmol / L. Such data may indicate pathology of the pituitary or adrenal gland. However, to clarify the diagnosis, additional studies are necessary.
If after taking a corticosteroid, the level of cortisol is from 50 to 140 nmol / l, then such indicators are considered doubtful. These data do not allow an unambiguous conclusion about the presence or absence of pathology. Unclear analysis results are called the gray zone. A small dexamethasone sample in such cases must be passed again.
False results
In some cases, the analysis gives distorted data. Not always a negative test result indicates a pathology of the endocrine glands. The use of certain drugs on the eve of the study may affect the performance of a small dexamethasone sample. A false-negative result may be noted when taking anticonvulsant medications. Such drugs contribute to the rapid removal of dexamethasone from the body. Therefore, before the test, it is necessary to exclude the use of such drugs. Also, false data can be noted in metabolic disorders.
How to lower cortisol
What to do with a negative result of a small dexamethasone test? In this case, it is recommended to retake the analysis. If the cortisol level still does not decrease after taking dexamethasone, then the doctor usually prescribes additional studies. A large dexamethasone test is required. This helps to differentiate the pituitary adenoma from adrenal gland diseases.
Special methods to reduce the concentration of cortisol do not exist. It is necessary to treat the underlying disease that caused hypercorticism. The level of the hormone normalizes only after eliminating the cause of its increase.