I also had intensely aching legs that lasted for a number of months and kept me up at night. Mine started probably two and a half years after my total thyroidectomy. All of my thyroid numbers were stable, and neither my PCP nor my endocrinologist had any idea what might be causing it. Being also of a an advanced age 😄I had no idea whether it was something just related to arthritis and aging. Here are some things I tried. I started wearing over the counter compression socks (not the real heavy duty ones) during the day and that made my legs feel much better during the day. I did not wear them at night but it seems like wearing them in the daytime reduced the aching at night as well. I asked my physical therapist at our last session (I was finishing up some physical therapy for my back) if he had any suggestions for the leg aching and he gave me some exercises to do with a pretty heavy duty stretch band. They only took about 5 minutes a day but I think that those helped as well. And I found a deep muscle therapist (and I mean deep) who worked intensely on my tight leg muscles over several months. The leg aching currently is mostly gone (knock on wood). My husband has had similar leg pain and his doctor had him massage an OTC magnesium gel into his legs. He swears by it. Maybe some of these ideas would be worth a try?