There are so many posts here that sound just like me. I too have dramatic extremes of temperature, (well that's to say the temperature that I
think my body is fluctuates wildly, with my actual body temp remaining quite constant, usually at 36.
something degrees).
I am often freezing cold, and nothing I do will make me warm. My many layers of clothes make my family laugh. And when I'm this cold I just huddle up on a sofa and I can't bring myself to move as moving will make me even colder! (Sounds strange, I know). Often only a really boiling hot bath will warm up my bones.. Except I don't know whether the bath is really boiling, or if I'm just perceiving it as boiling because my limbs are so cold!!
Other times I'm so boiling hot. It feels like it starts from inside my head, or even my nose and my ears. Sometimes it spreads to my whole body and is really uncomfortable. I get boiling when everyone else is cold, and my head feels all hazy and I feel kind of unwell. This hotness seems to be worse in the winter. And I think it's also worse during the second half of my cycle. I've been getting suddenly hot for several years, but this year and last year were the worst, and it seems to be much more extreme this year (sometimes I feel "too hot" for hours, or even all day long).
Last year I got a blood test to see whether I was starting the menopause (I'm 38), but that came out normal. I'm thinking that now these flushes are becoming more extreme then it probably is peri-menopause after all.
But now reading these other posts, I'm not sure if it's to do with autonomic dysfunction. It's all really confusing. My doctor thinks it's unlikely to be to do with the menopause as I still have regular periods, but I know that doesn't necessarily follow. And he doesn't know much about HMS, and didn't think it was relevant. I think I'm going to demand another hormone test as I'm finding it difficult to cope with these different extremes, and don't know where to start with them.
Sorry for the long post, I just wanted to get it all down, and say that it's interesting reading these stories. And I wondered if anyone had any comments or suggestions about how I can find out what's causing all of this craziness!

p.s. my description of getting suddenly hot seems to match up to typical menopausal "hot flush" descriptions that I've read online. Do
hot episodes caused by POTS manifest in the same kind of way?

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