Inclusion Criteria:

- Adult thyroid carcinoma patients who have had a total thyroidectomy, histology
confirmed by an MSKCC attending pathologist, and radioiodine remnant ablation.

- Adult thyroid carcinoma patients who have previously demonstrated radioiodine-avid
metastases and are about to undergo Thyrogen-assisted dosimetry at MSKCC.

- The patient and physician are planning to administer 131-I for therapy if persistent
radioiodine-avid metastases are present.

- Men and women of all races, ethnicities, and religious backgrounds are eligible.

- All subjects must have measurable disease, documented within the previous six months
by ultrasonography (US), MRI, or non-contrast CT scanning.

Exclusion Criteria:

- Thyroid cancer patients who do not have metastases.

- Thyroid cancer patients who have not demonstrated that their metastases concentrate
radioiodine.

- Patients who are under therapy for other active cancers.

- Anaplastic or Medullary thyroid carcinoma.

- Age less than 18 years.

- Patient who have received a therapeutic dose of radioiodine within the preceding nine
months will not be eligible.

- Patients who plan to withdraw from thyroid hormone prior to dosimetry.

- Patients who are pregnant.