Being positive for anti-TPO antibodies increases the risk of developing overt hypothyroidism in people with subclinical hypothyroidism or those at risk of developing thyroid dysfunction such as people with autoimmune diseases (e.g. type 1 diabetes), chromosomal disorders (e.g. Turner syndrome or Down syndrome) and people on certain medications such as lithium or amiodarone.3,5,7 If performed, and a person is anti-TPO antibody positive, there is no reason to repeat anti-TPO antibody testing.5 This evidence concerns the gene TPO and Down syndrome.