TPO and Hashimoto thyroiditis: Subsequently, anti-thyroid peroxidase (anti-TPO) antibodies at 16 and TSH receptor antibodies (TRAb) at 16 were obtained; although titers seem small, this may suggest long-standing Hashimoto's hypothyroidism; levels are not increased, likely due to atrophy of the gland (which is a phenomenon that can be seen in long-standing disease states).