About one week, give or take, after RAI, we are a lot more hyper than we were before due to the damaged thyroid cells dumping their hormone into the body all at once. After the dump, we then start to go hypo, some of us faster than others. I remember quite stunningly painful calf cramps post RAI. It would wake me up, and I would have to stretch out my heel to try to get it to go away. I tried stretching exercise (mild ones), warm baths, and extra bananas to avoid the painful episodes. I'm not sure how much good any of this did, other than psychologically. I attributed it to the fluctuation of thyroid levels. Hyper is very hard on muscles. Anyway, Kimberly's advice to talk with the doctor is good. But in the meantime, try to get your son to describe where the pain is. If it is his calf, have him lie down, and lift the offending leg and extend the heel to stretch out the hamstring. That usually provides rather immediate pain relief.
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