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Secondary hypertension

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Tanner Marshall.

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Video transcript

- [Voiceover] With primary hypertension you've got this high blood pressure. And well, ultimately the cause is unknown, right. We've got this big laundry list of risk factors that might contribute. But really we don't know exactly what did it. With secondary hypertension, the difference is we know exactly what's causing your blood pressure to rise. And we can pinpoint this other medical condition. So the hypertension happens secondary to some other disease. This form of hypertension accounts for only about 10% of hypertension cases. And so it's not that common, right, whereas the other 90% have primary hypertension. So let's sort of just dive right in to some of the common diseases that can lead to hypertension. All right, so renal diseases tend to be big time culprits for secondary hypertension. Where when we say renal, we're referring to the kidneys. With these, the kidneys don't function as they normally do. So since they're such huge players in regulating blood pressure through water and sodium regulation, if you've got some kind of underlying kidney problem, it can result in this inability to get rid of some fluid. And so more fluid in your body leads to higher plasma and blood volume and so higher blood pressure, because remember, flow and resistance in the blood vessels is directly related to blood pressure. So if you increase flow, you increase blood pressure. And one potential culprit for kidney diseases is polycystic kidney disease. By looking at poly, we know that that means many, right. And cystic refers to cysts which are like these fluid-filled sacs. So this is an inherited condition where you develop these fluid-filled sacs all around your kidneys. And if these guys get too big or there are too many of them, they can start to damage or disrupt your kidney's function, which can cause you to hold on to more fluid, and this will increase your blood pressure. Another renal disease is glomerular disease. And your glomeruli in your kidneys are like these filters for waste and salt or sodium. If these filters get swollen or just aren't working like they normally do, this can also increase your plasma volume and increase your blood pressure. Finally, you've got renovascular hypertension, where reno refers to your kidneys, right, and vascular are like the arteries that supply your kidneys with blood. So renovascular hypertension is usually due to some kind of narrowing of your arteries that supply your kidneys with blood. If and when these get narrow, they can't supply the kidneys with enough blood, right. When this happens, your kidneys think that there's not a lot of blood in your body and that maybe you're just dehydrated or something. And then they respond by trying to hold on to more fluid instead, which, as we know, causes your blood pressure to go up. Okay, so those were all having to do with your kidneys. But it doesn't always stem from the kidneys. Cushing syndrome, for example, has been known to cause secondary hypertension as well. With Cushing syndrome, you've got these high levels of circulating glucocorticoids, which are like these steroid hormones made by your adrenal cortex. So you've got all these glucocorticoids floating around in your bloodstream. And these facilitate sodium and water retention, which increases your plasma volume and your blood pressure. Another disease is called primary aldosteronism. This is where some factor, some thing, maybe like a tumor, causes your adrenal gland to release too much aldosterone. So this time you've got all this aldosterone circulating around your bloodstream. And what does that do? Well, it heads straight over to the kidneys and tells them to hold on to sodium and water. As we know all too well by now, this increases your plasma volume and so your blood pressure. The next one's a bit of a mouthful. It's pheochromocytoma. And this one again is a tumor that grows in the adrenal glands, which are also responsible for releasing hormones like norepinephrine and epinephrine which regulate your fight or flight response and can temporarily raise your blood pressure. Another one that's pretty important that you should be aware of is actually sleep apnea. Seems a little weird, right. Well, with sleep apnea, your breathing keeps like starting and stopping while you sleep. If you do this over and over and over again all night long, you end up not getting very much oxygen. When you don't get enough oxygen, your heart tries to pump harder and deliver more oxygen, which tends to sort of increase your flow at night, and therefore your blood pressure. So it's not uncommon to see a higher blood pressure at night for patients with sleep apnea. Obesity, though, it's also a risk factor for primary hypertension, can be a lone cause of secondary hypertension as well, since as your body weight increases, so does the amount of blood circulating around your body. This added plasma volume increases your flow and therefore increases your blood pressure. And finally, there's brain tumors and encephalitis. Both of these brain tumors and the inflammation of the brain or a/k/a encephalitis cause an increased pressure in your skull. This tends to decrease your blood delivery to parts of the skull, like your brain, pretty important. And since your brain is so important, your body tries to increase your blood pressure as well to sort of overcome this pressure in the skull and force more blood up into the skull and into the brain.