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Studying for a test? Prepare with these 2 lessons on Advanced endocrine system physiology.
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From terpenes to steroids part 2: Squalene, cholesterol, and steroids

Video transcript
Now that the light's at the end of the tunnel a little bit, I'm going to move a little bit more quickly through these reactions. So let me just copy and paste here. I'm going to clear a little bit more space. And so the body takes squalene, and through a series of ring-closing, or cyclization reactions, it makes cholesterol. And we consume some cholesterol in our diet, but our body also completes this reaction in the liver. So our body takes squalene and turns it into cholesterol in the liver. And cholesterol travels through our blood and it lives in the inside of cells and on their surfaces. In the case of endocrine organs that use steroid hormones to communicate, cholesterol can actually be altered to form the very characteristic steroid backbone. So let me draw that. So these are the four characteristic rings of the steroid backbone. As you can see, we are a really long way off, at this point, from the very beginning place that we started, which was that isoprene unit. Now that I've dragged you all the way from isoprene to the steroid backbone, I figured it was only fair that I showed you that this actually happens in your body, and there are actual steroids floating around your blood. I mentioned before that there are two important classes of steroid hormones in the body, and those are the sex hormones and the adrenal cortex steroids. With the sex hormones, I mentioned before estrogens, and we have estrasdiol and estrone. And you can see their steroid backbone. And those are predominantly made in the ovaries, and they're principally involved in secondary sex characteristics for females. And we have progesterone. It's the pregnancy hormone. It's involved in prepping the uterus, and it's also involved in maintaining a healthy pregnancy. And then we have androgens. And we have testosterone and androsterone. And similarly to the estrogens, those regulate the secondary sex characteristics, but more so in males. And they're predominantly made in the testes. Moving over to the adrenal cortex steroids, we have cortisone and cortisol. And those are the body's stress hormones, so they have a lot of the effects from anti-inflammatory to increasing carbohydrate metabolism. We also have aldosterone. Aldosterone is one of the main hormones that regulates our body's blood pressure and the fluid volume. And so I hope all these images make steroids a little bit more familiar to you, now that you've seen the classic backbone, and you know how to make it. Maybe the next time you find yourself enjoying the soothing relief of a menthol cough drop or a savory and delicious ginger snap cookie, you'll think about the countless number of terpenes that you're enjoying.