TPO and hypothyroidism: Phenothiazines with high Kc (e.g., chlorpromazine) may lead to iatrogenic hypothyroidism through increased protein-bound iodine.[19] At the thyroid gland level, chlorpromazine treatment has been shown to result in lowered serum T4 levels and decreased radioactive uptake of iodine by the thyroid gland in animal studies.[20,21] At the HPT axis level, chlorpromazine can cause changes in TSH levels by inducing formation of antithyroid antibodies.[18,22] Our patient, however, tested negative for thyroid stimulating immunoglobulin, thyroid peroxidase antibodies, and thyroglobulin antibodies.