Stimulated Thyroglobulin Testing Protocol

Methods of TSH Stimulation

The American College of Oncology recommends using recombinant human TSH (rhTSH) as the preferred method for stimulated thyroglobulin testing due to less morbidity and better quality of life, with thyroid hormone withdrawal being an alternative method that requires discontinuing levothyroxine therapy for 3-4 weeks to achieve adequate TSH stimulation (TSH >25-30 mIU/L) 1, 2, 3
Administration of 0.9 mg rhTSH intramuscularly for two consecutive days is a common protocol, with blood sampling for thyroglobulin measurement typically 72 hours after the second injection 2, 1, 4

Stimulated thyroglobulin testing is typically performed 6-12 months after initial treatment, or during follow-up for patients with previously negative TSH-suppressed thyroglobulin but at higher risk for recurrence, or when evaluating patients with suspicious findings on imaging or rising thyroglobulin levels 4, 5, 3, 6, 7, 1

A stimulated thyroglobulin level <1 ng/mL with negative antithyroglobulin antibodies indicates an excellent response to therapy, while levels between 1-10 ng/mL require continued monitoring and possibly additional imaging, and levels >10 ng/mL warrant consideration of radioiodine therapy and additional imaging 3, 1, 6, 8

The presence of thyroglobulin antibodies can interfere with thyroglobulin measurement, leading to falsely low results, and recent radioiodine administration can temporarily suppress thyroglobulin production, potentially leading to falsely low values 1, 4

For patients with a high likelihood of requiring radioiodine therapy, thyroid hormone withdrawal is suggested; otherwise, rhTSH is preferred, and in patients with distant metastases, consider steroid prophylaxis when using rhTSH stimulation 6, 8
Newer high-sensitivity thyroglobulin assays (<0.1 ng/mL) may reduce the need for stimulation testing in some low-risk patients 4, 5