My daughter who has Down syndrome is 15 and has had regular thyroid checks throughout her life, firstly via the NHS protocol for our area and latterly via our GP, as I became concerned. The results, including the ones via the GP were always "low but not at a level to treat yet". Yet towards the end of last year she became very low, was tired all the time, and suddenly and alarmingly her hair began to fall out. I'm sure many parents will have had the experience of not being believed when telling a nurse or doctor "but s/he's not usually like this". The hair loss, though, was something they could see and felt ready to act on, so it was a blessing in disguise. Despite the fact that her levels ware still "low but not at a level to treat yet", she was put on a low thyroid dose, which has subsequently been increased. Only a few months later, I have back my lively, happy girl and she has back her hair (though the new bits are short as yet, of course).
I write this to encourage other parents to persist if results of blood tests seem OK but you know something is wrong. It's so easy to put things down to "being a teenager" or something.
How can we help medical professionals to know that 'sluggish' isn't a natural state for anyone in good health, and that includes people with DS?