One study has reported Tg is eliminated through the liver and its half-life following total thyroidectomy has been reported to be about 65.2 hours. The Tg level was noted to decrease to less than 5-10 ng/ml 25 days after thyroidectomy, or after 7 to 10 half-lives in 11 patient samples5. Detection of Tg following the total thyroidectomy during long-term surveillance would therefore suggest persistent thyroid tissue.