Congenital adrenal hyperplasia
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Congenital adrenal hyperplasia
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Adrenal hyperplasia
Cushing syndrome p. 352
hyperaldosteronism and p. 354
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With congenital adrenal hyperplasia, congenital means present from birth, adrenals refer to the two adrenal glands that sit above the kidney, and hyperplasia refers to increased cell proliferation which leads to tissue growth.
So congenital adrenal hyperplasia is a disease where there are enlarged adrenal glands that are present at birth, and the reason for the adrenal enlargement is that there’s a deficiency in an enzyme involved with steroid production.
Now, each adrenal gland one has an inner layer called the medulla and an outer layer called the cortex which is subdivided into three more layers, the zona glomerulosa, zona fasciculata, and the zona reticularis.
The outermost layer is the zona glomerulosa, and it’s full of cells that make the hormone aldosterone.
The first step in aldosterone production is when an enzyme called cholesterol desmolase turns cholesterol into pregnenolone.
Pregnenolone is the precursor to all of the adrenal cortex hormones, sometimes called the steroid hormones.
Next, pregnenolone is turned into progesterone by the enzyme 3 beta-hydroxysteroid dehydrogenase.
Then, progesterone is turned into 11 deoxycorticosterone by the enzyme 21 hydroxylase.
11 deoxycorticosterone then gets turned into corticosterone by the enzyme 11 beta-hydroxylase.
And finally, corticosterone is turned into aldosterone by the enzyme aldosterone synthase.
Whew! That’s like going through the washing machine twice.
So the final result is aldosterone which is part of a hormone family called the renin-angiotensin-aldosterone system.
Aldosterone signals the kidney to reabsorb more Na+ into the blood and excrete more potassium.
When Na+ is reabsorbed, water also moves into the blood, which increases blood volume and blood pressure.
The middle layer of the adrenal cortex is the zona fasciculata, and the cells there make the hormone cortisol.
This process starts when pregnenolone and progesterone move into the zona fasciculata.
The enzyme 17 alpha -hydroxylase turns pregnenolone into 17 hydroxypregnenolone and turns progesterone into 17 hydroxyprogesterone.
Summary
Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders that affect the glandular cells in the adrenal cortex. This produces abnormal amounts of certain hormones, including cortisol, aldosterone, and androgen. These hormones are responsible for many essential functions in the body, including stress response, blood pressure, and kidney function.
There are several forms of CAH, each caused by a specific gene mutation. The most common form is called 21-hydroxylase deficiency, caused by a mutation in the CYP21A2 gene. 21-hydroxylase deficiency presents with masculinization in women and salt wasting, and hypoglycemia.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Monitoring of Therapy in Congenital Adrenal Hyperplasia" Clinical Chemistry (2010)
- "The Syndrome of 17,20 Lyase Deficiency" The Journal of Clinical Endocrinology & Metabolism (2012)