Adrenocorticotropic hormone (ACTH)
Why this test?
To detect dysfunction of the adrenal cortex (in combination with the determination of cortisol).
For differential diagnosis of the disease and various forms of Itsenko-Cushing's syndrome (in combination with the determination of cortisol).
To monitor the effectiveness of tumor treatment, including surgical treatment.
In what cases is it prescribed?
When conducting a test with corticotropin-releasing hormone.
If an ACTH-producing tumor is suspected.
With increased and decreased cortisol content in the blood plasma.
After transsphenoidal removal of corticotropinoma (an ACTH-producing pituitary tumor).
Adrenocorticotropic hormone (ACTH) is a hormone of the anterior lobe of the pituitary gland, which is secreted under the influence of corticotropin-releasing factor, which is secreted by the hypothalamus. Stimulates the biosynthesis and secretion of cortisol in the cortex of the adrenal glands. In addition to cortisol, to a lesser extent, ACTH ensures the synthesis of androgens and in physiological concentrations practically does not affect the production of aldosterone. ACTH levels are strongly influenced by stress, sleep, exercises and pregnancy.
Itsenko-Cushing syndrome is characterized by the presence of corticosteroma, or adrenal gland cancer, accompanied by hyperproduction of cortisol. At the same time, the secretion of ACTH decreases significantly.
Itsenko-Cushing's disease is characterized by increased functional activity of the pituitary gland due to hypertrophy of its cells or the development of a pituitary adenoma, which leads to excess production of ACTH and hyperplasia of the cortex of both adrenal glands. There is a simultaneous increase in the concentration of ACTH and cortisol in the blood, as well as an increase in the excretion of free cortisol and 17-ketosteroids in the urine.
Syndrome of ectopic production of ACTH is a pathological secretion of ACTH by a tumor of non-pituitary origin (most often bronchus cancer or thymoma, sometimes with medullary cancer of the thyroid gland, cancer of the ovary, breast, stomach and colon), which leads to increase the ACTH level in blood and as a result to hyperplasia of the adrenal cortex and increased cortisol secretion.
For differential diagnosis between Itsenko-Cushing's disease and ectopic production of ACTH, in which the level of ACTH in blood plasma is increased, a test with corticotropin-releasing hormone is used. The secretion of ACTH after the introduction of this hormone increases significantly in case of Itsenko-Cushing's disease patients.In case of ACTH-producing tumors of non-pituitary localization, the level of ACTH does not change significantly, since the cells of these tumors do not have receptors for corticotropin-releasing hormone.
With Addison's syndrome - it occurs due to destructive processes of primary insufficiency of the adrenal cortex - the production of glucocorticoids, mineralocorticoids and androgens decreases, in response to which the secretion of ACTH increases and its rhythm is disturbed.
Secondary and tertiary adrenal insufficiency - the result of damage to the pituitary gland or hypothalamus - is accompanied, respectively, by a decrease in the concentration of ACTH and secondary hypoplasia or atrophy of the adrenal cortex. A test with corticotropin-releasing hormone allows to assess the residual reserve of ACTH. When the pituitary gland is damaged, the secretion of ACTH in response to the introduction of this hormone does not increase, but if the hypothalamus is damaged (due to which the production of corticotropin-releasing hormone is reduced or stopped), the introduction of this hormone will lead to an increase in the secretion of ACTH and cortisol.
Nelson's syndrome is characterized by the presence of a pituitary tumor, an increase in the concentration of ACTH and secondary adrenal insufficiency and develops after the total removal of the adrenal glands in Itsenko-Cushing's disease.
Thus, determining the concentration of ACTH in the blood is necessary (in combination with a cortisol test) to detect disorders in the hypothalamus-pituitary-adrenal system.