The presence of metastatic tumors was associated with a significant decrease in the activity of iodothyronine deiodinase (DIO1), with an average reduction of 11-fold, an 8-fold decrease in the expression of the TFF3 gene, a 4-fold decrease in the expression of the thyroid peroxidase (TPO) gene, and a 2.6-fold decrease in the expression of the SLC26A7 (the sulfate anion transporter) gene. This evidence concerns the gene TPO and metastatic neoplasm.