Despite the determined half-life of Tg, in a retrospective study with 36 patients with low-risk papillary thyroid carcinoma, the unstimulated Tg level fell to < 0.5 ng/ml after 6 months postoperatively in only 61%, and after 2 years postoperatively in 100% of the patients6. No prospective studies have yet determined the nadir of the Tg level post thyroidectomy. In our personal clinical experience, unstimulated serum Tg levels may be found undetectable 6 to 12 weeks following a total thyroidectomy.