Hi
I have been on HRT for quite a few years as I entered the menopause early. A few months back I realised I had run out of tablets and didn't get round to renewing my prescription for a while. At this point I was training quite hard for a half - my pace and stamina improved massively which I put down to increased and harder training. Running seemed more effortless than it had ever been in all the years I have been running. Got round to picking up my new prescription and within a week I was back to a much slower pace, stuggling with hills, and just hating my runs 
Is this my imagination? Anyone have experience of anything like this?