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Steroids and Bile Acids: Steroid Hormone Metabolism

by Kevin Ahern, PhD
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    00:02 Now cholesterol, as I said, is a precursor of the steroid hormones and steroid hormones play very important roles in our body.

    00:11 There are 5 classes of steroid hormones.

    00:14 The first of which we called the progestogens; because, cholesterol is converted into progestogens. One of which is progesterone as you see on the screen.

    00:22 And the progestogens are the precursors of the other steroid hormones.

    00:26 Now notice I am saying progestogens and it spells like it's progestogens and it's actually spelled in both ways so the "O" and A" in progestogens are equivalence balance.

    00:39 In any way the progestogens can be converted into the other classes of steroid hormones and these are all classes of hormones many related compounds.

    00:47 One is the glucocorticoids that you can see here. The other is the mineralocorticoids that you can see here and the third is the androgens here.

    00:57 Now the androgens themselves which are the male sex hormones are the precursor of the female hormones known as the estrogens.

    01:04 And in going from the androgens on the right to the estrogens to the left we see that the lower left ring on the androgens has a single double bond. But the lower left ring on the estrogen is a benzene ring.

    01:18 That involves creation of an aromatic ring and that's a very unusual reaction in biology.

    01:24 This is about the only place where an aromatic ring is created by an enzyme.

    01:31 And the enzyme that creates this is known as an aromatase.

    01:34 An aromatase catalyzes this conversion.

    01:37 Now, I tell you that; because, this is an important for enzyme for health purposes.

    01:42 Many tumors are estrogen sensitive. Meaning that when they bind to estrogens are stimulated to grow.

    01:50 These tumors are more of a factor in women although men do have some estrogens within their bodies as well.

    01:56 If your doctor senses a tumor or detects a tumor in you, one of the first test will be on that tumor is to see if it is estrogen sensitive; because, if the tumor is estrogen sensitive then the doctor is going to use as part of their treatment an aromatase inhibitor to stop the production of estrogens.

    02:15 And if that happens then many times the tumor can be very effectively controlled.

    02:22 In addition to being the precursors of the steroid hormones, the cholesterol is also a precursor of important compounds called bile acids.

    02:30 Now I have shown three bile acids on the screen and you can see that of course their structures resemble that of cholesterol.

    02:37 Bile acids play a very important role in solubilizing fat in your digestive system. So they come from bile and bile is there to help emulsify fat, fat soluble vitamins and cholesterol.

    02:51 So the first step in that process that I showed you on the screen earlier the movement of cholesterol in the body, the very step happens before the cholesterol, and the fats and the fat soluble vitamins get transferred across the intestinal wall. The first step is they get emulsified in water.

    03:10 Well emulsification is just a fancy way of saying "making them dissolve" and that's what soaps do with grease and that's what bile acid do with these compounds.

    03:17 In this lecture, I have gone through the synthesis of cholesterol from very simple compounds like acetyl-CoA and how cholesterol can be converted into other compounds that are important in our body such as the steroid hormones and the bile acids.

    03:33 I hope in the presentation the message you take away is that while cholesterol is associated with some very detrimental health problems, cholesterol is necessary for functioning in the animal body.


    About the Lecture

    The lecture Steroids and Bile Acids: Steroid Hormone Metabolism by Kevin Ahern, PhD is from the course Lipid Metabolism.


    Included Quiz Questions

    1. Aromatase
    2. Estrogen synthetase
    3. Estrogen cyclase
    4. Androgen hydrolase
    5. Androgen decarboxylase
    1. Progestagens are the precursors of all of the other ones
    2. Synthesis of androgens from estrogens requires aromatase
    3. Mineralocorticoids are precursors of all of them except progestagens
    4. Glucocorticoids include aldosterone

    Author of lecture Steroids and Bile Acids: Steroid Hormone Metabolism

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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