TPO and goiter: This compound is a known inhibitorof thyroperoxidase (TPO), an enzyme essential for synthesizing thyroidhormone. TPO catalyzes several reactions,including iodination of tyrosyl residues in thyroglobulin and subsequentoxidative coupling to yield thyroxine (T4) and triiodothyronine (T3). Inhibition of such TPO functions may reduceblood TH levels, resulting in thyroid hyperplasia and developmentalabnormalities or neurological dysfunction. Human data show severe clinical hypothyroidism with associated goiter.