Corticotropin – Properties And Effects
Corticotropin, also known as adrenocorticotropic hormone (ACTH), is a polypeptide hormone consisting of 39 amino acids. Small doses (approximately 10 mg) are produced daily in the pituitary gland that stimulate the adrenal glands.
Thus, ACTH stimulates two of the three areas of the adrenal cortex that secrete cortisol and glucocorticoids. However, it also stimulates the reticular zone that produces androgens. Its biological function is to stimulate cortisol secretion. In this way, the body will produce more corticotropin during tense, stressful situations.
The synthesis of corticotropin
The pituitary gland synthesizes ACTH in response to the release of the corticotropin-releasing hormone (CRH) in the hypothalamus. Similarly, the adrenal glands produce a hormone called cortisol that helps the body deal with stress. This is because cortisol is needed to live. In this way, the levels in the blood remain under control.
Measurement of corticotropin levels
The purpose of an ACTH analysis is to use it as an indicator of pituitary function and to detect any problems in the adrenal glands. It is useful in the differential diagnosis of the following diseases:
- Addison’s disease
- Adrenogenital syndrome
- Cushing’s disease
As cortisol levels rise, ACTH levels usually fall. When cortisol levels fall, ACTH levels tend to rise.
However, there may be a high level of ACTH and a low level of cortisol or vice versa. This may be due to a problem in the adrenal glands. Low levels of both ACTH and cortisol may be due to a problem with the pituitary gland.
When ACTH production is excessive, it may be due to an overactive pituitary gland or, in some cases, a tumor in the lungs.
Both ACTH and cortisol levels vary throughout the day. The amount of corticotropin is usually at its highest early in the morning, between 06:00 and 08:00. However, the lowest levels occur in the afternoon, between 18:00 and 23:00.
If your doctor thinks it is necessary, they will either measure your ACTH level in the morning or in the afternoon. Usually they also measure cortisol levels at the same time. Corticotropin is released in pulses, so blood levels can vary from one minute to the next.
Normal corticotropin values
Normal corticotropin values for a blood sample taken early in the morning are less than 80 pg / ml or 18 pmol / L. However, they are lower than 50 pg / ml or 11 pmol / L in the afternoon.
What does an ACTH level higher than normal mean?
When corticotropin levels are higher than normal it may indicate the presence of diseases such as:
- Addison’s disease: Here the adrenal glands do not produce enough cortisol.
- Adrenogenital syndrome : In this case, the adrenal glands do not produce enough hormones.
- Multiple endocrine neoplasia type 1: This occurs when one or more endocrine glands are overactive or when they form a tumor.
- Cushing’s disease: In this case, the pituitary gland produces too much corticotropin, which is usually due to a benign pituitary tumor.
- Ectopic Cushing’s disease: This is a rare type of tumor that occurs in the lungs, thyroid or pancreas and it produces too much corticotropin.
A lower than normal level of corticotropin
When corticotropin levels are lower than normal, they may indicate the presence of the following diseases :
- Hypopituitarism – this indicates that the pituitary gland is not producing enough hormones, such as corticotropin.
- A tumor in the adrenal glands – here the presence of the tumor generates too much cortisol.
- Treatments with glucocorticoid drugs inhibit the production of corticotropin.
Conclusion
The measurement of corticotropin values can be affected by many factors, such as when the blood sample is taken during the day. For this reason, you will need to take into account the medical information from other tests, especially those related to cortisol levels in the blood.
