I don't sweat much, but I'm pretty intolerant to heat (tends to trigger panic/anxiety, too). I seemed even more intolerant when I took Effexor for 2 months recently, so it definitely seems like it could be med-related (I'm now on Cymbalta and not noticing as much of an effect). Hormones can certainly play a role, too--when I was pregnant my heat intolerance was much worse and it was like I was having hot flashes. The first couple days of my period are like that, too.