TPO and autism: Enzymes such as thyroid peroxidase (TPO) or tyrosine hydroxylase are inhibited or down-regulated, leading to reduced thyroid hormone or dopamine release and signaling [137,204], which can lead to alterations in neurodevelopment, neurotoxicity [205], and recently reported increases in Attention Deficit/Hyperactivity Disorder (ADHD) and potentially autism [206,207].