They say that the best way to learn something is to teach it, so that’s exactly what I’m going to do right now. But because you don’t want to know the boring stuff I’ll just tell you the interesting bits. The bits that will actually make you go aahhhh. Well, they made me go aahhhh, I don’t know about you. Perhaps if this kind of stuff interested you you’d actually be studying medicine. Perhaps you are, perhaps that’s why you’re here, you want to see life from a similar but different perspective.
Whatever, the fact is that you must be just about as bored as I am.
Okay, todays nugget of detail. Have you been watching flashforward? I’m up to episode 6 or something, then Demand Five kept cutting out on me so I had to stop, which was irritating in itself but anyway that’s not why I’m here. There was that one episode, where they diagnosed Addisons disease basied on the fact that in his flashforward the white man had somehow become black. Why does Addisons cause someone to become black?
Basically, Addisons is a disease caused by having too little cortisol. The secretion of cortisol is regulated by two things. When cortisol levels rise this is first detected in the hypothalamus in the brain, which releases CRH (corticotrophin releasing hormone). CRH goes on to stimulate the pituitary gland (which is also in the brain), causing it to secrete a substance called ACTH. The ACTH goes on to stimulate the secretion of cortisol from the adrenal cortex.
Anyway, in Addisons disease the adrenal cortex basically gets annhihalated by the body, i.e. in technical terms it is an autoimmune destruction of the body’s own cortex cells. As a result, the amount of cortisol it secretes decreases, which feeds back to the hypothalamus which releases more CRH, so the pituitary releases more ACTH. But due to the damaged adrenal gland, the amount of cortisol doesn’t rise up again, which means that moreand more ACTH is produced.
That’s all well and good, I can hear you crying, but how does it turn a white man black?
Well, when the ACTH is synthesised, it actually has within it a sequence of amino acids that is very similar to another protein called Melanocyte Stimulating Hormone (MSH). As a result, ACTH can, when it is in excess, bind to MSH receptors on melanocytes. And what melanocytes do is increase skin pigment, such that to wild excess, it could turn a white man black.
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