Adrenocorticotropic hormone: what it is, features and functions

We can define hormones as a group of chemical messengers which, together with neurotransmitters and pheromones, directly influence the functioning of organs and tissues at a certain distance from where they were generated. Every multicellular being synthesizes hormones, including plants.

Although most of the most important organs are synthesized in the endocrine glands, almost all organs found in animals produce some type of hormone. These interesting biological molecules are stimulated or inhibited by other hormones, plasma concentrations of ions or nutrients, neurons and mental activity, and environmental changes, among other factors.

Thus, a sort of “biochemical cascade” occurs which responds to both intrinsic and extrinsic stimuli of the individual. Today we come to talk to you about adrenocorticotropic hormone, one of the most important in terms of stress and borderline management situations. Don’t miss it.

    What is adrenocorticotropic hormone?

    From a physiological point of view, the adrenocorticotropic / adrenocorticotropic hormone (ACTH) is a hormone of a polypeptide nature, produced by the pituitary gland, which stimulates the adrenal glands, Which regulate the stress response through the synthesis of corticosteroids and catecholamines.

    ACTH is produced by the pituitary or pituitary gland, an endocrine gland found in vertebrates (located at the base of the brain) that secretes hormones responsible for regulating homeostasis and growth, as these inhibit or promote the synthesis of other hormonal substances in different organs of the body. Next, we will examine the chemical properties of this curious polypeptide.

    Chemical structure

    The adrenocorticotropic hormone is a polypeptide, that is, a type of molecule formed by the union of 10 to 50 amino acids, the basic structures of proteins. Specifically, ACTH is made up of 39 amino acids, the sequence does not change between species. It is as follows:

    Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Try-Gly-Lys-Pro-Val-Gly-Lys-Lys-Arg-Arg-Arg-Pro-Val-Lys-Val-Tyr-Pro- Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe.

    Each of these diminutives refers to a specific amino acid, the first two being serine and tyrosine, for example. It should be noted that, of the 39 amino acids that make up this polypeptide, only 13 of them have a clear and known biological function.

    Action mechanism

    Let’s try to keep it simple, because describing a metabolic pathway can be a very tricky task. Corticotropin releasing hormone (CRH) is released from the hypothalamus, the region of the brain below the thalamus.

    CRH stimulates the pituitary gland, described above, to release ACTH. It is released by the bloodstream and travels to the adrenal cortex (located in the kidneys), where it stimulates certain glands to synthesize cortisol and androgens. Interestingly, cortisol has inhibitory activity because its presence in the blood decreases the production of CRH by the hypothalamus, thus producing negative feedback activity.

    CRH (hypothalamus) → ACTH (pituitary) → Cortisol and androgens (adrenal glands)

    Physical and psychological stress promotes the synthesis of ACTH, which results in more circulating cortisol. This is a clear adaptive mechanism: faced with a dangerous situation, all possible compounds must be mobilized for the defensive response to be the most effective. We explain this mechanism in the following lines.

      Functions of the adrenocorticotropic hormone

      We have briefly defined the chemical structure and metabolic pathway of ACTH. At this point, it’s time to dissect the functions of this curious hormone:

      • Respond to stressful situations.
      • Fight infections that occur in our body.
      • Regulates blood sugar.
      • Maintain blood pressure.
      • Regulates metabolism, i.e. the relationship between energy expenditure and consumption in the individual.

      Basically, these are the functions of the adrenocorticotropic hormone, however all these bases are supported in specific physiological processes. For example, cortisol and other glucocorticoids promote events such as hyperglycemia, that is, the presence of high blood sugar. Elevated glucose levels in a dangerous situation respond to a clear evolutionary mechanism, as the muscles thus have more immediate energy to burn in demanding physical activities, such as escaping from danger.

      On another side, glucocorticoids also cause lipolysis, Whereby fatty lipids from adipose tissue are mobilized to other tissues in the body to serve as an immediate source of energy. Protein catabolism and bone resorption also serve the same purpose.

      On the other hand, androgens promote spermatogenesis and have certain anabolic effects on muscles and bones. The summary is as follows: Cortisol and androgens (and therefore ACTH) are mechanisms that promote our responses to dangerous situations, because they mobilize nutrients so that our tissues can act quickly and efficiently.

        associated pathologies

        Unfortunately, and like all tissues in the human body, there are certain dysfunctions that can trigger an excessive or deficient presence of the adrenocorticotropic hormone. Here are a few briefly.

        1. Addison’s disease

        It is a disorder that occurs when the adrenal glands do not synthesize enough hormones. Elevated ACTH levels are correlated with this pathology in some patients, In which abdominal pain, chronic diarrhea, darkening of the skin, dehydration, dizziness, extreme weakness and weight loss may be observed, among many other clinical signs.

        2. Congenital renal hyperplasia

        Another disease that can be detected by the concentration of adrenocorticotropic hormone in the blood is congenital renal hyperplasia. As in Addison’s disease, the adrenal glands reduce the synthesis of one of the following hormones: cortisol, mineralocorticoids, such as aldosterone, which regulate sodium or potassium levels; or androgens. In many cases of congenital renal hyperplasia, there is a deficiency of cortisol and an overproduction of androgens..

        3. Cushing’s syndrome

        Unlike the previous pathology, this syndrome occurs when the body is exposed to high levels of cortisol for a long time. Clinical signs and symptoms may vary depending on the amount of hormone present in the blood, but among them are the following: weight gain and fatty tissue deposits, pronounced stretch marks on the skin of the abdomen, thighs , breasts and arms, thin faithful, slow healing and acne.

        What happens to too low ACTH levels?

        Reduced levels of adrenocorticotropic hormone in the blood lead to poor synthesis of cortisol in the adrenal glands.. This promotes a state of hypoglycemia (remember that the hormone promotes the release of blood glucose), weakness and fatigue.

        On the other hand, a decrease in the synthesis of ACTH usually results in a lower proportion of androgens, which manifests itself mainly in women, with a decrease in libido and a lack of pubic axial hair. In men, the effect is not quantifiable, since a large amount of testicular androgens not directly related to the adrenal glands is synthesized.

        The ACTH blood test is performed when a lack or excess of cortisol is suspected in the patient’s bloodstream. Normal morning levels of this hormone are around 9-52 pg / ml (2-11 pmol / L). Due to the human circadian rhythm, the levels of these hormones (cortisol and ACTH) are much higher in the morning and decrease throughout the day, reaching a minimum during the night. As you can see, fatigue is not only mental, but responds to a physiological process regulated by hormonal intermediates.

        summary

        The adrenocorticotropic hormone is essential for understanding stress responses in living things, but it also has many other functions. Without going any further, androgens are also linked to it, which is why hair pubis, libido, spermatogenesis and other processes related to gender and sex are conditioned by it.

        Spaces like this show that the body is nothing more than a cascade of reactions, whether hormonal, nervous, or based on chemical compounds. Ultimately, we can draw a map with a clear origin and head, in this case the response to stressful situations and certain sexual components.

        Bibliographical references:

        • ACTH. medlineplus.gov. Retrieved December 31, from https://medlineplus.gov/spanish/pruebas-de-laboratorio/hormona-adrenocorticotropica-acth/.
        • Adrenocorticotropic hormone, you and your hormones. Retrieved December 31, from https://www.yourhormones.info/hormones/adrenocorticotropic-hormone/#:~:text=Adrenocorticotropic%20hormone%20(ACTH)%20is%20made,part)%20of%20the%20adrenal% 20gland .
        • Allen, MJ and Sharma, S. (2020). Physiology, adrenocorticotropic hormone (ACTH). StatPearls [Internet].
        • Elkinton, JR, Hunt, AD, Godfrey, L., McCrory, WW, Rogerson, AG and Stokes, J. (1949). Effects of treatment with pituitary adrenocorticotropic hormone (ACTH). Journal of the American Medical Association, 141 (18), 1273-1279.
        • Congenital adrenal hyperplasia, Mayoclinic.org. Retrieved December 31, from https://www.mayoclinic.org/es-es/diseases-conditions/congenital-adrenal-hyperplasia/symptoms-causes/syc-20355205.
        • Adrenocorticotropic hormone, National Cancer Institute (NIH). Retrieved December 31, from https://www.cancer.gov/espanol/publicaciones/diccionario/def/hormona-adrenocorticotropica.
        • Pearson, OH and Eliel, LP (1950). Use of pituitary adrenocorticotropic hormone (ACTH) and cortisone in lymphoma and leukemia. Journal of the American Medical Association, 144 (16), 1349-1353.

        Leave a Comment