Adrenocorticotropic hormone: definition, functions and associated diseases.

We explain all the characteristics of this hormone linked to stress reactions.

The human body functions in the same way as a production chain. In order to obtain a final result (in this case a physical or bodily response) a series of previous reactions must first occur. For example, when we perceive the symptoms of stress, a series of chain reactions have already taken place within our organism.

One of the agents that make this chain reaction possible is adrenocorticotropic hormone.. A hormone of complex functioning and with a multitude of functions of which 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 belongs to the category of tropic polypeptide hormones and although it is mainly related to stress processes and reactions, it is also used as a medicine and diagnostic factor in a large number of organic conditions.

Discovered in 1933 by the American biochemist Evelyn M. Anderson, this hormone has been the object of study of innumerable investigations, due to the great number of functions and effects it has on the organism, as well as its complex way of acting.

We now know that adrenocorticotropic hormone is one of the main agents involved in the functioning of the hypothalamic-pituitary-adrenal axis and its production has traditionally been associated with a biological stress response.

In addition, this hormone plays a fundamental 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, ACTH promotes the release of hormones such as adrenaline and noradrenaline..

However, as mentioned above, the main function of ACTH is to increase cortisol and corticosterone levels in the blood. This happens as a response to stress and its main effect on the organism 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 body.. It itself functions differently throughout the day, generating higher peaks of ACTH in the morning, especially upon awakening, and declining throughout the day. This is known as the diurnal rhythm of adrenocorticotropin.

As for the possible therapeutic effects of adrenocorticotropin, it is often used in the treatment of inflammation. In the form of an Anti-Inflammatory drug, it is administered in cases of inflammatory conditions such as rheumatoid arthritis, lupus erythematosus and ulcerative colitis.

Production and regulation

The synthesis of adrenocorticotropic hormone 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 gland 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 corticotropin-releasing hormone, which stimulates the activity of the pituitary gland to secrete more adrenocorticotropin into the bloodstream.

However, when the adrenal glands detect an excess of this hormone, which causes an increase in blood cortisol levels, there is an automatic decrease in adrenocorticotropin-releasing hormone, so the amount of adrenocorticotropin in the bloodstream begins to decrease. This is what 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 lead to a wide range 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 adrenocorticotropin deficiency.

1. Excess ACTH in the blood

The effects of an excess of adrenocorticotropic hormone are a direct consequence of increased cortisol levels in the blood. 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 diseasePituitary adenoma: This condition is caused by a cancerous tumor or adenoma located in the pituitary gland and is usually related to abnormal ACTH levels.
• Tumor formations located outside the pituitary gland known as an ectopic adrenocorticotropic hormone tumor.
• Addison's diseasecharacterized by abnormally low levels of cortisol but excessively high levels of ACTH.
• Congenital adrenal hyperplasiaa genetic disorder distinguished by inadequate production of cortisol and/or aldosterone.

2. ACTH deficiency

Conversely, it may happen that the person experiences a deficit of adrenocorticotropic hormone also due to the appearance of tumor formations or as a side effect of radiotherapy or surgery on the pituitary.

In this case, the main conditions associated with this deficit are:

• Adrenal insufficiencyACTH: the adrenal glands stop producing ACTH as they should, which causes a decrease in adrenal androgens.
• Cushing's diseasein addition to an excess of ACTH, it can also be related to a deficit of ACTH.
• Clinical conditions of the pituitary gland such as hypopituitarism.

Although these are the main clinical conditions related to adrenocorticotropin, there is a large list of other conditions in which this hormone has a special role. Among them we find:

• Small cell carcinoma
• Nelson's syndrome
• West's syndrome or infantile spasms
• Postorgasmic 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.