Adrenocorticotropic hormone: definition, functions and associated diseases
The human body works just like a production line. To obtain an end result (in this case a physical or bodily response) a series of prior reactions must first take place. For example, when we perceive the symptoms of stress, a series of chain reactions have already taken place inside our body.
One of the agents that make this chain reaction possible is the hormone adrenocorticotropic . A hormone with complex functioning and a multitude of functions that we will talk about throughout this article.
What is adrenocorticotropic hormone?
Also known as ACTH, adrenocorticotropic hormone or corticotropin, this hormone secreted by the pituitary gland falls into the category of tropical polypeptide hormones and although it is mainly related to stress processes and reactions it is also used as a drug and diagnostic factor for a large number of organic conditions.
Discovered in 1933 by the American biochemist Evelyn M. Anderson, this hormone has been the object of innumerable investigations, due to the great number of functions and effects that it possesses in the organism, as well as for its complex form of action.
For the moment we know that the adrenocorticotropic hormone is one of the main agents involved in the functioning of the hypothalamic-pituitary-adrenal axis and its production has been traditionally associated with a biological stress response.
In addition, this hormone plays a key role in the regulation and release of other hormones known as steroids. By stimulating the activity of the adrenal and suprarenal glands, ACTH promotes the release of hormones such as adrenaline and noradrenaline .
However, as mentioned above, the main function of the corticotropic hormone is to increase the levels of cortisol and corticosterone in the blood. This happens as a response to stress and its main effect on the body is related to the metabolism of fats, carbohydrates, proteins and blood pressure.
Likewise, the role of the adrenocorticotropic hormone is closely related to the circadian rhythms of our organism . It itself functions differently throughout the day, generating higher peaks of ACTH in the morning, especially at the time of awakening, and which decline throughout the day. This is known as the daytime rhythm of adrenocorticotropin.
As for the possible therapeutic effects of adrenocorticotropin, it is often used in the treatment of inflammation. It is produced in the form of an anti-inflammatory drug and is administered in cases of inflammatory conditions such as rheumatoid arthritis, lupus erythematosus and ulcerative colitis.
Production and regulation
Adrenocorticotropic hormone synthesis takes place in the anterior lobe of the pituitary gland, also known as the adenohypophysis. However, the regulation and control of its release is linked to three interconnected regions of our body: the hypothalamus, the pituitary and the adrenal glands. This structure is known as the hypothalamic-pituitary-adrenal axis.
When ACTH levels in the blood are lower than usual, the small group of cells in the hypothalamus release a hormone known as ACTH, which stimulates the activity of the pituitary gland to secrete more adrenocorticotropic hormone into the bloodstream.
However, when the adrenal glands detect an excess of this hormone, which causes an increase in blood cortisol levels, a decrease in ACTH is automatically produced, so the amount of adrenocorticotropic hormone in the bloodstream begins to decrease. This is known as a negative feedback loop .
Pathologies associated with ACTH
Due to its role in a large number of activities and functions of our body, abnormal levels of adrenocorticotropic hormone can cause a great deal of diseases and clinical conditions .
These ACTH-related diseases vary significantly depending on whether they are caused by increased levels of this hormone in the blood or, conversely, whether they are caused by adrenocorticotropic deficiency.
1. Excess ACTH in blood
The effects of excess adrenocorticotropic hormone are a direct consequence of increased blood cortisol levels. Although this increase in corticosteroid hormones does not necessarily pose a health hazard, abnormally high levels are often associated with the following conditions:
- Cushing’s disease -This condition is caused by a cancerous tumor or adenoma located in the pituitary gland and is often associated with abnormal ACTH levels.
- Tumor formations located outside the pituitary gland known as ectopic adrenocorticotropic hormone tumor.
- Addison’s disease : characterized by abnormally low levels of cortisol but excessively high levels of ACTH.
- Congenital adrenal hyperplasia : a genetic disorder distinguished by inadequate production of cortisol and/or aldosterone.
2. ACTH deficit
Conversely, the person may experience a deficit of adrenocorticotropic hormone also due to the appearance of tumor formations or as a side effect of radiation therapy or surgery on the pituitary.
In this case, the main conditions associated with this deficit are
- Adrenal insufficiency : the adrenal glands stop producing ACTH as they should, causing a decrease in adrenal androgens.
- Cushing’s disease : in addition to an excess of ACTH, it can also be related to a deficit of it.
- Clinical conditions of the pituitary gland such as hypopituitarism.
Although these are the main clinical diseases related to adrenocorticotropin, there is a long list of other conditions in which this hormone has a special role. Among them we find:
- Small cell carcinoma
- Nelson’s Syndrome
- West syndrome or infantile spasms
- Post-Thorgasmic Disease Syndrome
Bibliographic references:
Backers A, Stevenaert A, Foidart JM, Hennen G and Frankenne F (1991). Placental and Pituitary growth hormone secretion during pregnancy in acromegazic women. J Clin Endocrinol Metab 71:725.
Guyton-Hall (2001). Treatise on Medical Physiology.10th ed., McGraw-Hill-Interamericana.