What Causes Hot Flushes After Total Hysterectomy?

Good evening.. I am a 63 year old female. I had a full hysterectomy 15 years ago. Went on HRT - premarin 625gm for approx. 8 yrs...dropped then to a lower dosage 325gm for the next 4 yrs...then that dosage every second day for approx. the following three years. Have stopped now, MY QUESTION: Why would I still get hot flushes?? 1. At my age and 2. after having a full hysterectomy. I do not take any other medication other than over the counter RED KRILL OIL (active joints) and the odd voltarin tablet usually as a preventative before whipper snipping!!!
I am a coeliac, being diagnosed within the 12 months after my surgery. So, of course, I eat exceptionally well and within the accepted weight range. 173 and 75kilos.
With thanks,
Peta