Definitely make sure to check since it's easy to test and easy to treat, but remember that it could be both. What blows is that some doctors can become really dismissive of the idea that you might have something like ADHD if your chart already carries a different label (thyroid, personality disorders, depression, etc.) so watch out for that, it can be a challenge to get them to take it seriously.

The cognitive bias of humans to "explain away" is one of my great pet peeves.

Generally you’ll have both a blood test for thyroid dysfunction and possibly a sleep study because chronic sleep deprivation also presents with adhd like lack of focus.

My thyroid was checked multiple times and always was fine. Now (recently) I got diagnosed with ADHD.