Letrozole side effects

I would assume so yes. Coming off HRT would mean that your body goes into menopause and then the letrozole stops oestrogen from being produced anywhere else in your body (mainly fat cells I think.

I am mid-40s and have been on zoladex implants to put me into a medica menopause and then exemestane on top. I will be 50 when I come off everything and I was really worried about my ovaries firing back up again and going through the menopause a 2nd time. My oncologist said that is extremely unlikely. I had chemo, then ovaries stopping for such a long time would mean them coming bck to life at 50 would be a bit of a miracle!

They must have thought you were already menopausal as letrozole, exemestane etc is only to be used for post-menopausal women.

I had a hysterectomy just prev to HRT. 

If you've had a hysterectomy then what you're going through just now is your menopause, which was being kept away by HRT. I don't think anything would change once you come off letrozole, though hopefully things will just continue to improve. You won't go through another menopause at that stage as your body is getting used to the lack of oestrogen now.

I don't think I could do the menopause twice!!