Adrenocorticotropic hormone, metabolic effects

Corticotropin (adrenocorticotropic hormone, ACTH) regulates the function of the adrenal cortex and has numerous other effects on metabolism. It contains 39 amino acids in the form of a random coil, owing to the presence of several proline residues that prevent helix formation. Species differences are seen in amino acids 25-39 the rest of the ACTH molecule is identical in all animals and humans. The first 24 amino acids are responsible for all of the biological action of ACTH synthetic human ACTHj 24 is known as cosyntropin. 

Corticosteroids and adrenocorticotropic hormone have been widely used for the treatment of ulcerative cohtis and Crohn s disease, given parenterally, orally, or rectally. Corticosteroids are believed to modulate the immune system and inhibit production of cytokines and mediators. It is not clear whether the most important steroid effects are systemic or local (mucosal). Budesonide is a corticosteroid that is administered orally in a controlled-release formulation. The drug undergoes extensive first-pass metabolism, so systemic exposure is thought to be minimized. Immunosuppressive agents such as azathioprine, mercaptopurine (a metabolite of azathioprine), methotrexate, or cyclosporine are sometimes used for the treatment of IBD. ... 

Some of the rare causes of metabolic alkalosis due to potassium depletion are those found in subjects with either Cushing s syndrome, primary aldosteronism, or Bartter s syndrome. In Cushing s syndrome, the potassium ions and alkalosis are related to increased mineralocorticoid activity resulting from an increase in adrenocorticotropic hormone (ACTH), cortisol, deoxycorticosterone, and corticosterone. In primary aldosteronism, the effects of increased aldosterone are manifest on the distal tubule of the kidney. In Bartter s syndrome, the basic abnormality appears to be a defect in the reabsorption of chloride in the ascending limb of loop of Henle, leading to loss of potassium (12). 

The actions of hormones are very diverse. Some, e.g. glucagon, have specific and clearly defined effects on the metabolism of particular tissues. Others such as growth hormone and the sex hormones have more general effects on growth and development while the tropic hormones stimulate their target tissues to secrete further hormones. For example the adrenocorticotropic hormone (ACTH), which is produced in the anterior pituitary, promotes the synthesis and release of glucocorticoids by the adrenal cortex. A list of some of the hormones and their effects on metabolism is given in Table 24.1. 

In other situations, stress factors such as emotional disturbances, fasting, starvation, or diabetes, are signals to the pituitary gland to release adrenocorticotropic hormone (ACTH), which acts both alone on tissues and stimulates secretion of other stress hormones by the adrenal glands. The net effects of these stress-responsive hormones are the tearing down (catabolism) of fat, muscle, and/or bone tissues, so as to provide essential nutrients for metabolism. 

Leboeuf, B., and G. F. Cahill jr. Studies on rat adipose tissue in vitro. VIII. Effect of preparations of pituitary adrenocorticotropic and growth hormone on glucose metabolism. J. biol. Chem. 236, 41 (1961). 

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