ACTH

Cross references:  HPA Axis   Cortisol   

Adrenocorticotropic hormone (Wiki) 
    "Adrenocorticotropic hormone (ACTH), also known as 'corticotropin'', is a polypeptide tropic hormone produced and secreted by the anterior pituitary gland. It is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological stress (along with corticotropin-releasing hormone from the hypothalamus). Its principal effects are increased production and release of corticosteroids and, as its name suggests, cortisol from the adrenal cortex."  



Adrenocorticotropic Hormone (ACTH, corticotropin)  




Adrenocorticotropic hormone, as its name implies, stimulates the  Adrenal Cortex . More specifically, it stimulates secretion of Glucocorticoids such as  Cortisol , and has little control over secretion of aldosterone, the other major steroid hormone from the  Adrenal Cortex .

ACTH is secreted from the anterior Pituitary Gland in response to  Corticotropin-releasing hormone (CRH)   Hormone  from the  Hypothalamus . Corticotropin-releasing hormone (CRH) is secreted in response to many types of  Stress, which makes sense in view of the " Stress  management" functions of   Glucocorticoids Corticotropin-releasing hormone (CRH) itself is inhibited by   Glucocorticoids , making it part of a classical negative feedback loop.

Additional information on the role of ACTH in regulation of adrenal steroid secretion is presented in the sections on the adrenal gland and glucocorticoids.

Within the  Pituitary Gland , ACTH is produced in a process that also generates several other hormones. A large precursor protein named proopiomelanocortin (POMC, "Big Mama") is synthesized and proteolytically chopped into several fragments as depicted below. Not all of the cleavages occur in all species and some occur only in the intermediate lobe of the  Pituitary Gland .

The major attributes of the hormones other than ACTH that are produced in this process are summarized as follows:

  • Lipotropin: Originally described as having weak lipolytic effects, its major importance is as the precursor to beta-endorphin.
  • Beta-endorphin and Met-enkephalin: Opioid peptides with pain-alleviation and euphoric effects.
  • Melanocyte-stimulating hormone (MSH): Known to control melanin pigmentation in the skin of most vertebrates.

Index of: The Hypothalamus and Pituitary Gland


ACTH-like molecules in gastropod molluscs: a possible role in ancestral immune response and stress.  (PubMed)  - 1991 
Only abstract available online. 
    "The presence of immunoreactive ACTH molecules on phagocytic cells from the freshwater snails Planorbarius corneus and Lymnaea stagnalis was shown by cytofluorimetric analysis. The role of ACTH in phagocytosis and in the release of biogenic amines, two biological responses that may be taken as ancestral types of immune response and 
Stress , respectively, has also been evaluated. ACTH markedly increased the phagocytosis of Staphylococcus aureus by P. corneus haemocytes and caused the release of biogenic amines from such cells into the serum. These data, as well as tracing the ancestral physiological role of ACTH, favour the hypothesis that immune and neuroendocrine systems share a common evolutionary origin."  









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