Cholesterol steroid hormones from

Many steroidogenic tissues synthesize steroid hormones from the cholesterol provided by LDL particles. 

Steroidogenesis synthesis of steroid hormones from cholesterol. Interactions of Fat Metabolism Pathways ... 

Adrenodoxin Hie enzyme is used in the synthesis of steroid hormones from cholesterol. It is used for the introduction of oxygen atoms into cholesterol in the biosynthetic pathways for aldosterone, the glucocorticoids, and the sex hormones. 

B. Both pregnenolone and progesterone are intermediates in the synthesis of steroid hormones from cholesterol. 7-Hydroxycholesterol is an intermediate in bile salt synthesis, and aldosterone is a mineralocorticoid produced well beyond the branch point for the synthesis of the adrenal and gonadal steroids. Retinoic acid is derived from vitamin A. 

Biosynthesis of steroid hormones from cholesterol. The different pathways occur to varying extent in adrenals, gonads, and placenta. The systematic names for cytochrome P-450 enzymes, namely CYP followed by a number, are given in parentheses. CYPI1B2 and CYP17 possess multiple enzyme activities. [Reproduced with permission from P. C. White and P. W. Speiser, Congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Endocrine Reviews 21,245 (2000).]... 

Examples of endogenous biotransformation reactions catalyzed by cytochrome P450 electron transport systems include the synthesis of steroid hormones from cholesterol (Chapter 12) and the conversion of vitamin D3 to its biologically active form 1,25-dihydroxyvitamin D3. 

Steroids are a femily of lipid molecules that includes cholesterol, steroid hormones, and bile salts. These amphipathic molecules (containing both hydrophobic and hydrophilic regions) are derived from two-carbon acetyl-CoA... 

Bile acids are derived from cholesterol and have detergent properties which aid in fat digestion and absorption (Figure 18.4). Bile acid synthesis is the major metabolic end product of cholesterol, accounting for about half of the 800 mg/day that is made in the body. By contrast, synthesis of steroid hormones from cholesterol requires only about 50 mg/day of cholesterol. Although the body synthesizes about 400 mg of bile acids per day, closer to 20-30g of bile acids per day are secreted into the upper small intestine. To meet this need, the body recycles bile acids from the lower small intestine to the liver via enterohepatic circulation. 

Pregnenolone is derived from cholesterol and is the precursor of all other steroid hormones. For example, pregnenolone is coverted to progesterone by oxidation of the hydroxyl group to a ketone and isomerization of a double bond (see here). Synthesis of other steroid hormones from progesterone is shown in Figure 19.24. 

In the early 1930 s, when the prime research aim was the commercial synthesis of the sex hormones (whose structures had just been elucidated), the principal raw material available was cholesterol extracted from the spinal cord or brain of cattle or from sheep wool grease. This sterol (as its 3-acetate 5,6-dibromide) was subjected to a rather drastic chromic acid oxidation, which produced a variety of acidic, ketonic and hydroxylated products derived mainly by attack on the alkyl side-chain. The principal ketonic material, 3j -hydroxyandrost-5-en-17-one, was obtained in yields of only about 7% another useful ketone, 3 -hydroxypregn-5-en-20-one (pregnenolone) was obtained in much lower yield. The chief acidic product was 3j -hydroxy-androst-5-ene-17j -carboxylic acid. All three of these materials were then further converted by various chemical transformations into steroid hormones and synthetic analogs ... 

Testosterone, the principal male sex steroid hormone, is synthesized in five steps from cholesterol, as shown below. In the last step, five isozymes catalyze the 17/3-hydroxysteroid dehydrogenase reactions that interconvert 4-androstenedione and testosterone. Defects in the synthesis or action of testosterone can impair the development of the male phenotype during embryogenesis and cause the disorders of human sexuality termed male pseudohermaphroditism. Specifically, mutations in isozyme 3 of the 17/3-hydroxysteroid dehydrogenase in the fetal testis impair the for-... 

FIGURE 25.43 The steroid hormones are synthesized from cholesterol, with intermediate formation of pregnenolone and progesterone. Testosterone, the principal male sex hormone steroid, is a precursor to /3-estradiol. Cortisol, a glucocorticoid, and aldosterone, a mineralocorticoid, are also derived from progesterone. 

Steroid hormones are produced by the adrenal cortex, testes, ovaries, and placenta. Synthesized from cholesterol, these hormones are lipid soluble therefore, they cross cell membranes readily and bind to receptors found intracellularly. However, because their lipid solubility renders them insoluble in blood, these hormones are transported in the blood bound to proteins. Furthermore, steroid hormones are not typically preformed and stored for future use within the endocrine gland. Because they are lipid soluble, they could diffuse out of the cells and physiological regulation of their release would not be possible. Finally, steroid hormones are absorbed easily by the gastrointestinal tract and therefore may be administered orally. 

Plant sterols such as sitosterol and camposterol, as by-products from vegetable oils at prices of about 15 kg-1, are also important starting materials for the production of steroid hormones. A new application is the cholesterol lowering property of these sterols esterified with fatty acids (with a production of about 10000 t a 1). They can be found in the margarine Becel pro-active of Unilever. A Finnish equivalent is Benecol, which contains stands such as sitostanol and campostanol, sterols having the 5,6-double bound hydrogenated, also esterified with fatty adds [33]. 

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