from Part III - Management of specific disorders
Published online by Cambridge University Press: 04 May 2010
Characteristics of congenital adrenal hyperplasia and medical treatment
Overview of the adrenal gland
The adrenal glands are triangular in shape, measuring 3 cm × 5 cm × 1 cm, and are sited above each kidney. The central adrenal medulla is responsible for production of adrenaline and noradrenaline. This portion of the adrenal may be dysplastic early in the natural history of congenital adrenal hyperplasia (CAH) and in time the hyperplastic cortex takes over and the medulla becomes atrophic (Merke et al., 2000a). Absence of the adrenal medulla is thought to be of no consequence because catecholamines are also produced throughout the nervous system.
The adrenal cortex is responsible for the production of three types of steroid; glucocorticoids (cortisol), mineralocorticoids (aldosterone) and androgens. CAH refers to defects in one of the enzyme steps in the adrenal steroidogenesis pathways, which mediate the alterations to the basic four carbon rings in the substrate cholesterol.
Cholesterol is the substrate for all steroid hormones (Miller, 1991). It is taken up by adrenal cells via receptors for low and high density lipoprotein (LDL and HDL, respectively), the abundance of which is increased by the action of adrenocorticotrophic hormone (ACTH). The scheme of adrenal steroid production is presented in Fig. 24.1. The conversion of cholesterol to cortisol occurs in five stages.
Cholesterol side-chain cleavage (cholesterol desmolase; gene designation: CYP11A1) is the rate-limiting step in the cortisol pathway. Cholesterol is delivered by StAR protein (steroidogenic acute regulatory protein) to the mitochondria where the side-chain cleavage enzyme is located. The electron transfer process, which results in removal of the side chain at C20, produces the cortisol precursor pregnenolone.
[…]
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.