Cau 28: hormon tuyen can giap: ban chat, tac dung, dieu hoa bai tiet va UDLS

*) ban chat hoa hoc cua parathormon (PTH): PTH o dang hd trong mau la 1 polypeptid co 84 a.a, trong lg ptu la 9500

*) tac dung cua PTH :

PTH dong vtro quan trong trong dieu hoa Cm ion calci va ion phosphat cua huyet tg. Duoi td cau PTH Cm ion calci huyet tg tang nhung ngc lai Cm phosphat lai giam. PTH thuc hien Cnang nay = cac td tren xuong than va ruot

- tac dung cua PTH tren xuong : PTH lam tang muc giai phong ion calci tu xuong vao mau = cach tdong len cac TB xuong, Tb tao xuong va TB huy xuong

+ tac dung len TB tao xuong va TB xuong : mang TB xuong va Tb tao xuong co cac receptor tiep nhan PTH. Phuc hop receptor - PTH hoat hoa bom calci va ion calci dc bom tu dich xuong vao dich ngaoi bao

+ tac dung len TB huy xuong : tren mang TB huy xuong ko co receptor tiep nhan PTH nen TB huy xuong ko chiu td kick thick truc tiep cau PTH ma phai thong qua cac tin hieu chuyen tu Tb xuong va TB tao xuong. do vay td tren TB huy xuong cua PTH thg xay ra cham hon.

- tac dung tren than

+ lam giam bai xuat ion calci o than

+ lam tang tai hap thu ion calci va magie o ong than db o ong luon xa va ong gop

+ lam giam tai hap thu ion phosphat o ong luon gan do do lam tang dao thai ion phosphat ra nc tieu

- tac dung len ruot: Do PTH hoat hoa qtrinh tao 1,25 dihydroxycholecalciferol tu vitamin D3 nen PTH co nhung td len ruot nhu sau:

+ tang tao enzym ATPase o diem ban chai cua TB bmo nmac ruot

+ Tang tao chat van taI ion calci o nmac ruot

+ tab

g hoat tinh enzym phosphatase kiem o Tb nmac ruot

-> Tang hap thu ion calci va phosphat o ruot

*) Dieu hoa bai tiet : Cm PTH bthuong trong mau vao khoang duoi 50pg/ml. PTH dc bai tiet nhieu hay it tuy thuoc vao Cm ion calci va phosphat trong mau db la Cm ion calci. chi can giam nhe ion calci trong mau thi tuyen can giap d• bai tiet PTH. Nuu tinh trang lam giam Cm ion calci keo dai thi tuyen can giap se no to, doI khi to gap 5 lan or hon. ngc lai neu Cm ion calci trh mau tang thi hd va kcik thuoc cua tuyen can giap se giam.