Part of my self-thyroid test is a memory check. When my thyroid first became low, if someone walked by me and said hi at work, I wouldn't say anything back because I could not recall one single persons name. I went on thyroid and could remember all of them. Went off thyroid memory went again. Went back on and my memory came back. Also my reflexes got really slow and I had to be careful when driving when I was low.