Corticotropin: What It Is And How It Works

Corticotropin, also called adrenocorticotropin or corticotropin (ACTH), is a polypeptide hormone made up of 39 amino acids. It is produced by the pituitary gland and stimulates the adrenal glands. The daily production is small, around 10 mg a day.

ACTH stimulates two of the three areas of the adrenal cortex where the glucocorticoids cortisol and corticosterone are secreted, although it also stimulates the reticular zone that produces androgens. Its biological function is to stimulate the secretion of cortisol. In this way, in times of stress or tension, the body produces more corticotropin.

When is corticotropin (ACTH) synthesized?

ACTH is synthesized in the pituitary in response to the release of corticotropin-releasing hormone (CRH) by the hypothalamus. For their part, the adrenal glands produce a hormone called cortisol that helps the body handle stress. Cortisol is necessary for life, so the levels of this hormone in the blood are controlled.

What is the purpose of measuring corticotropin levels?

The ACTH test is used as an indicator of pituitary function and to detect a problem in the adrenal glands. It is useful in the differential diagnosis of the following pathologies:

• Addison’s disease.
• Congenital adrenal hyperplasia.
• Cushing’s syndrome.

When cortisol levels rise, ACTH levels normally go down. When cortisol levels drop, ACTH levels normally rise.

However, there may be a high ACTH level and a low cortisol level, or vice versa. This could be caused by a problem with the adrenal glands. However, low levels of ACTH and cortisol could be caused by a problem with the pituitary gland.

When ACTH production is excessive, it can be caused by an overactive pituitary or sometimes a tumor in the lung.

Both ACTH and cortisol levels change throughout the day. Corticotropin normally reaches its highest level early in the morning, between 6:00 a.m. and 8:00 a.m. However, the lowest level occurs in the afternoon, between 6:00 p.m. and 11:00 p.m.

In case your doctor finds it necessary, he will measure your ACTH levels in the morning or in the afternoon. Most often, while ACTH is measured, cortisol levels are also measured. Corticotropin is released in pulses, so its blood levels can vary from minute to minute.

What are normal corticotropin values?

Normal values for corticotropin blood sample taken in the early morning are less than 80 pg / mL or less than 18 pmol / L. However, for the afternoon measurement they are less than 50 pg / mL or less than 11 pmol / L.

What can a higher than normal ACTH level mean?

When corticotropin levels are higher than normal, it can indicate the presence of diseases such as :

• Addison’s disease : the adrenal glands that don’t make enough cortisol.
• Congenital adrenal hyperplasia : Not enough hormones are produced by the adrenal glands.
• Multiple endocrine neoplasia type I : occurs when one or more endocrine glands are overactive or have formed a tumor.
• Cushing’s disease : occurs when the pituitary is producing too much corticotropin hormone, which is caused by a benign tumor of the pituitary, normally.
• Ectopic Cushing syndrome : this is a rare type of tumor that can appear in the lung, thyroid or pancreas and that produces too much corticotropin.

What can indicate a lower than normal ACTH level?

When corticotropin is below normal values, it can indicate the presence of pathologies such as :

• Hypopituitarism: indicates that the pituitary gland is not producing enough hormones, such as corticotropin.

• Adrenal gland tumor : The presence of the tumor causes too much cortisol to be produced.
• The glucocorticoid treatment drugs make corticotropin production is inhibited.

Conclution

The measurement of corticotropin levels can be affected by many factors, such as the time of day the extraction is done. For this reason, it is advisable to take into account medical information from other tests, especially the level of cortisol in the blood.