Same thing with my aunt. Had a thyroid test while she was going through ivf and now takes thyroxine daily. Thing is though, she was a maximum of maybe 20 or 30lb overweight (maybe up to a UK size 12, she's now down to an 8) and still swam 3 times a week and took her dogs out walking. A thyroid condition explains being a little overweight,  it doesn't excuse being a death fat.