Hey everyone!
Trying to type up a paper here and can't really find any info on this, wondering if anyone can help me out

Why does smoking, use of HRT, Birth control, etc. increase the coagulability of the blood that leads to DVT's / PE's

I'm not sure they're the same mechanism. Hypercoagulability in smokers is thought to be related to increased levels of thromboxane A2 (via the COX enzyme system). See article here: http://circ.ahajournals.org/cgi/content/full/112/7/1024

I think the hypercoagulability from contraceptives stems from the progesterone, but I don't recall hearing of a proposed mechanism. I found one paper suggesting that oral estrogens induce activated protein C resistance, thereby creating a hypercoagulable state, but I'm sure there are other theories out there (http://ahavj.ahajournals.org/cgi/content/full/atvbaha;01.ATV.0000087141.05044.1F). Another paper says progestins "decrease anticoagulant proteins and increase procoagulant proteins" (top of pg 193; http://humupd.oxfordjournals.org/cgi/reprint/5/3/191.pdf)

I hope that helps some! (I'm still not sure of the correct answer)