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Aldosterone synthase, also called steroid 18-hydroxylase, corticosterone 18-monooxygenase or P450C18, is a steroid hydroxylase cytochrome P450 enzyme involved in the biosynthesis of the mineralocorticoid aldosterone and other steroids. The enzyme catalyzes sequential hydroxylations of the steroid angular methyl group at C18 after initial 11β ...
Hypoaldosteronism causes low sodium (hyponatremia), high potassium (hyperkalemia), and metabolic acidosis, a condition in which the body produces excess acid.These conditions are responsible for the symptoms of hypoaldosteronism, which include muscle weakness, nausea, palpitations, irregular heartbeat, and abnormal blood pressure.
The genes encoding aldosterone synthase and 11β-hydroxylase are 95% identical and are close together on chromosome 8. In individuals with GRA, there is unequal crossing over so that the 5' regulatory region of the 11-hydroxylase gene is fused to the coding region of the aldosterone synthase. [citation needed]
18-Hydroxylase (aldosterone synthase) – mineralocorticoid synthesis; 21-Hydroxylase – corticosteroid synthesis; Cytochrome P450 (CYP1, 2, 3) – estrogen metabolism; Hydroxysteroid dehydrogenases (and ketosteroid reductases) 3α-Hydroxysteroid dehydrogenase – androgen, progestogen, and neurosteroid synthesis and metabolism
Corticosterone is converted to aldosterone by aldosterone synthase, found only in the mitochondria of glomerulosa cells. Glomerulosa cells are found in the zona glomerulosa , which is the most superficial region of endocrine cells in the adrenal cortex .
It may be increased in 17α-hydroxylase deficiency, [4] in aldosterone synthase deficiency, [5] in primary aldosteronism, and may also indicate a histologic variant of the aldosteronoma. [4] Excessive secretion of 18-OH-DOC can cause mineralocorticoid excess syndrome, although these cases are very rare.
Primary hyperaldosteronism has a number of causes. About 33% of cases are due to an adrenal adenoma that produces aldosterone, and 66% of cases are due to an enlargement of both adrenal glands. [1] Other uncommon causes include adrenal cancer and an inherited disorder called familial hyperaldosteronism. [6]
Steroid 21-hydroxylase is a protein that in humans is encoded by the CYP21A2 gene.The protein is an enzyme that hydroxylates steroids at the C21 position on the molecule. [10] [11] Naming conventions for enzymes are based on the substrate acted upon and the chemical process performed.