No change that, its very important. Do you know what your thyroid does? I think most people would say it does something with your endocrine system. (And what does your endocrine system do? Can you answer that part?) It actually does a lot more. There is a simplified version attached here but basically it controls a lot of your body. Its your largest endocrine gland.
Wikipedia says "The thyroid gland controls how quickly the body uses energy, makes proteins, and controls how sensitive the body should be to other hormones." Or think of it this way it "stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate." So basically it runs your body.
So I don't have one. I haven't had one for thirty years. I can tell you with low thyroid your fingernails are brittle, your feel lethargic, and can't remember anything. If you are too much thyroid (take two pills in one day instead of one because you forgot you already took one - did that ONCE) and you feel like you are on a marathon and can't get off. Your heart pounds and your head is going a mile a minute.
I am in a constant struggle to monitor my thyroid levels - too high, too low, my doctors tweak it and then I feel the results. Right now I think they are too low, my doctor thinks they are fine. In the meantime, I can blame my lack of brain cells on chemo brain but maybe I can blame thyroid stuff too.
On that uninspired note, I get to go round up all the doctor phone numbers I need to call today and go to work on a Monday. I hate working on Mondays and Fridays. One benefit to my schedule now, is I usually work from home on Mondays and Fridays but that's not happening this week. I have to work both Monday and Friday this week.