Updated September 15, 2005
Researchers reporting in the
Journal of Clinical Endocrinology & Metabolism were evaluating the accuracy of a single recombinant human (rh)TSH-stimulated serum thyroglobulin (Tg) test -- this is a thyroglobulin test while on the drug Thyrogen. Thyrogen is a drug that enables thyroid cancer patients to avoid having to withdraw from all thyroid hormone drugs, and become hypothyroid in preparation for a scan.
The researchers looked at 107 differentiated thyroid cancer patients, and separated them according to their initial rhTSH-Tg levels. Group 1 had a Tg less than 0.5, group 2 had Tg of 0.6–2.0, and group 3 had a Tg greater than 2. The patients were evaluated over the period of a year to five years, and Tg was measured during thyroid hormone suppression, after rhTSH and/or after complete thyroid hormone withdrawal.
What they discovered was that in 81% of those patients who had an initial or follow-up rhTSH-Tg greater than 2, tumor was found. The researchers concluded that:
"A single rhTSH-Tg greater than 2 ng/ml predicts persistent tumor, although no value entirely excludes future recurrence."
Patients at risk of recurrence, and especially those who had an rhTSH-Tg greater than 1, should get repeated TSH-stimulated testing.
Patients who had a rhTSH-Tg less than 0.5 ng/ml without Tg antibody are so unlikely to have a recurrence that "frequent imaging and TSH-stimulated Tg testing are unnecessary."
Source: Kloos and Mazzaferri, "A Single Recombinant Human Thyrotropin-Stimulated Serum Thyroglobulin Measurement Predicts Differentiated Thyroid Carcinoma Metastases Three to Five Years Later" The Journal of Clinical Endocrinology & Metabolism Vol. 90, No. 9 5047-5057. See PubMed abstract
