Can children have hyperthyroidism? My son’s been anxious, can’t sit still and can’t concentrate. I thought maybe adhd, but the doctor says no. Now he’s losing weight, even though he eats a lot. Maybe more than usual. Could he have hyperthyroidism? He’s 6.

Yes, . Yes, this is possible. Grave's disease is relatively rare at this age, but certainly not unheard of. It is easy to test for with a simple blood test. That being said, out of a thousand children with the symptoms your child has at age 6, perhaps one would have hyperthyroidism as a cause.
Yes. Hyperthyroidism can occur at any age. His symptoms suggest hyperthyroidism. I recommend seeing his physician to get tested.
Yes to child thyroid. Children can indeed have thyroid disorders! i became very tired at age ten. The doctor suspected mono, but it turned out to be hypothyroidism. If it can go down, it can certainly go up! talk to your child's pediatrician and ask for blood work to rule it out. Don't back down! rapid pulse is common in hyperthyroidism too, and can exhaust your heart after a couple of years. He could have adhd too.