Accordingly, these guidelines focus on the diagnosis and management of genetic disorders of thyroid hormone transport, metabolism, and action comprising resistance to thyroid hormone β (RTHβ), resistance to thyroid hormone α (RTHα), monocarboxylate transporter 8 (MCT8) defects, selenoprotein deficiency, and iodothyronine deiodinase 1 defects. This evidence concerns the gene TG and hereditary disease.