Serum Thyroglobulin Measured With a Second-Generation Assay in Patients Undergoing Total Thyroidectomy Without Radioiodine Remnant Ablation: A Prospective Study

Abstract

Follow-up consisting of the measurement of nonstimulated serum thyroglobulin (Tg) combined with neck ultrasonography is recommended for patients with papillary thyroid carcinoma without indication for radioiodine ablation. There is no recommendation of thyrotropin suppression during this follow-up. New-generation Tg assays have been increasingly used, but few studies involve patients submitted only to thyroidectomy and they have several limitations. The objective of this prospective study was to define expected concentrations of nonstimulated Tg measured with a second-generation assay after total thyroidectomy in the absence of tumor. Serum Tg was measured using a second-generation assay in 69 patients without tumor and serum thyrotropin between 0.5 and 2 mIU/L, 3, 6, 12, and 24 months after total thyroidectomy. All patients had undetectable anti-Tg antibodies. Serum Tg was undetectable in 44.4%, 57%, 62.5%, and 62.1% of the patients 3, 6, 12, and 24 months after thyroidectomy, respectively, and was ≤0.5 ng/mL in 60.3%, 80%, 90.6%, and 90.9% of patients. All patients had a Tg≤2 ng/mL 6 months after thyroidectomy, and 97% had a Tg≤1 ng/mL 24 months after surgery. There was no case of Tg conversion from undetectable to detectable and none of the patients presented an increase in Tg. An important decline in serum Tg occurred between 3 and 6 months after total thyroidectomy. One year after surgery, Tg was undetectable in approximately 60% of the patients and was ≤2 ng/mL in all of them.