Transcript for:
Calcium, PTH, and Their Interactions

so to First really understand our basic path uh how what calcium does we need to really go back and look at the basic pathophysiology so this is your parathyroid gland remember there's four of them they lie directly behind the thyroid uh in these glands you have these little cells uh within these cells there are uh parathyroid hormone which is packaged up in little vesicles being ready to released to be released in addition you have calcium receptors these receptors are inhibitory therefore uh if calcium levels rise um these receptors are turned on and remember they're inhibitory so the release of pth is inhibited if the calcium levels are low then it's not activated and pth is released so what does p pth do pth affects several systems if this release of pth it release it affects our bones our kidneys and indirectly our gastrointestinal system so what does it do in each of these systems well in the bone it it leads to reabsorption of the bone which results in increased calcium and phosphorus if you think back to your basic path of physiology remember that calcium phosphorus is what the bone matx is actually made out of um in the gut what happens is due to a uh Rel uh vitamin D which comes from the kidneys is made in the kidneys and indirectly this goes to the gut and causes uh you to absorb in the gut and this will increase your calcium and phosphorus levels um so you're going to increase the absorption of both in the kidneys what happens is the pth causes the reabsorption of calcium and the excretion of of phosphorus so therefore your calcium goes up and your phosphorus goes down um so how does all this work so if the kidneys are working then remember that the kidneys always win that is to say if there's too much parathyroid hormone calcium uh will Elevate and phosphorus will fall um and the opposite will occur when there is uh there'll be a decrease in calcium and a rise in phosphorus um another thing that can affect um these pth levels is a granulous disease uh these are diseases in which you kind of have a fake yeah elevation of vitamin D and some of the examples are TB and sarcoid so that's just something to keep in the back of your mind um another thing that can affect these these levels are albumin uh calcium is bound by albumin as a matter of fact only about 1% of it is ionized calcium or what is actually free in the blood so therefore if you have alumin can affect your um calcium levels and this is an inverse uh reaction so for every uh a normal alumin is four normal calcium is 10 for every one point that your albumin is down this leads to an increase in your calcium level of 0.8 so for example let's say you have an albumin of three and a calcium of 9.2 uh you can quickly calculate in your head that that calcium is actually 10 so while an alumin a low albumin um a low albumin associated with a low calcium the calcium actually may be normal um regardless uh one thing to remember is that you know all these things abuin uh sarcoid disease but particular your pH uh think disease processes that cause a low ph and high pH pth uh these are the things that can affect our um our calcium levels and we'll discuss just a little bit more of that on the next slide