Could anyone give me their experiences with Underactive Thyroid weight gain? My numbers went back to normal a few weeks ago following a few months being Overactive (yey), and my weight went back to what it was pre Overactive Thyroid, but I’m becoming slightly paranoid about switching to Underactive. I put on a few pounds at Christmas like everyone does, went back to my usual 5-2 way of eating during January, but the weight is pretty static and I have put a pound on today (Saturday is my usual weighing day!). So I am trying to find out what to look for, the Endo had told me it’s possible for someone to switch from Over to Under, although a little rare. I’m wondering how quickly weight gain occurs when you tip into Underactive, should I look out for a pound a week or something more sudden? The only other thing that I’ve noticed is achy legs but only in bed at night, which of course could be something different. I realise it’s a tricky question as everyone is different, plus I am 54 this year so age may gradually have an impact on my weight!! Boo! Anyone’s early experiences would be really appreciated. Thank you in advance.