A dexamethasone test is used to diagnose depression . It is based on the fact that depression increases the level of corticosteroids and cortisol. After the introduction of 1 mg. dexamethasone, the amount of ACTH (adrenocorticotropic hormone) decreases, and the level of cortisol remains high.
The table provides information on the physiological basis of the dexamethasone test.
|Place of hormone production||The name of the hormone||Functions|
|Hypothalamus||Corticotropin Release Factor (CRF)||Increases the secretion of ACTH|
|Pituitary gland (anterior lobe)||ACTH (adrenocorticotropic hormone)||Enhances the production of cortisone and corticosterone|
|Adrenal glands (cortex)||Corticosterone , cortisol.||Increases the level of glucose, fatty acids, enhances urine filtration, increases blood pressure.|
In the 1980s, the dexamethasone test was used more often. Its sensitivity was 44% and specificity 93% for depression ( Arana et Baldessarini ). If the patients had other mental disorders, then the specificity scores decreased. With panic attacks and anxiety up to 88.2%, with schizophrenia – 86.9%, alcoholism – 80%.
A number of researchers have recorded positive results of the dexamethasone test in obsessive – compulsive disorder.
Gender and age did not affect the dexamethasone test scores, but in the elderly, its values could be higher.
Antipsychotics, antidepressants, lithium preparations do not affect the test results, and barbiturates, benzodiazepines, anticonvulsants can lead to a false positive result.
With alcohol intoxication and taking caffeine, false positive results are also noted.
Similar data are found for brain tumors, diabetes mellitus, Addison’s disease, Itsenko-Cushing’s disease, cardiovascular failure, infectious diseases, trauma, pregnancy. This is an indication that the dexamethasone test has relative specificity.
But nevertheless, the dexamethasone test indicators normalize upon recovery from depression, and its increased indicators may reflect a negative prognosis and an increased risk of suicide.
The dexamethasone test is of great diagnostic value in psychotic depression and bipolar affective disorder.
The sensitivity of the test is associated with a hereditary predisposition to depression. The biochemical basis of the test is a change in the sensitivity of receptors to glucocorticoids, which leads to a low level of ACTH in response to the introduction of corticotropin- releasing factor. There is also no suppressive effect on cortisol levels with the administration of dexamethasone (a synthetic glucocorticoid). Thus, despite some disadvantages, the dexamethasone test can be used in the treatment of depression.