Hey Matilda!
YES!! That definitely happened to me.
As you know, my only symptom is insomnia.
In February this year I started doing more cardio. As a result, I lost about 3 kilos. I wasn't taking HRT at the time, but I was experiencing intermittent sleep disturbances; the occasional early morning waking for about one hour every now and then. Before February I would get on average about 5-6 days per month where this would happen; I would wake at 3AM for about one hour.
It was annoying but manageable, since most of the time I slept pretty well.
Around April (when I had lost the extra weight), it increased to 9-10 times per month until in July, I had a real slump and things went pear shaped (hence starting HRT).
I'm convinced it was the weight loss that did it. The less padding we have, the less we are able to store estrogen (and I am pretty skinny anyway, so the extra drop in kilos was probably the straw that broke the camel's back).
Maybe it's time to go up to 50mcg?