To assess whether the patient preparation procedure for (131)I scintigraphy could be streamlined, we evaluated the time course of thyroid-stimulating hormone (TSH) elevation after total thyroidectomy or after discontinuation of thyroxine (T(4)) in patients with thyroid cancer.
Methods: The clinical records of 284 patients with well-differentiated thyroid cancer were reviewed. All patients had undergone total thyroidectomy. Two groups of patients were evaluated. The immediate postoperative group consisted of 176 patients who were not given thyroid hormone replacement after surgery because of planned postoperative (131)I therapy. The surveillance group consisted of 108 patients in whom T(4) replacement was stopped (without triiodothyronine [T(3)] replacement) in preparation for surveillance whole-body (131)I scintigraphy. We recorded the first TSH measurement and number of days after surgery or without thyroid hormone for each patient.
Results: In the immediate postoperative group, TSH levels obtained 6-65 d (median, 17 d) after surgery ranged from 18.2 to 194.8 micro IU/mL (median, 46.6 micro IU/mL). The TSH values exceeded 30 micro IU/mL in 89% of patients evaluated at 1-2 wk, in 88% of those evaluated at 2-3 wk, and in 90% of those evaluated after 3 wk. In patients discontinuing T(4) (without T(3) replacement), TSH levels obtained from 6 to 35 d (median, 20 d) later ranged from 23.4 to 214.5 micro IU/mL (median, 61.1 micro IU/mL). The TSH levels exceeded 30 micro IU/mL in 100% of patients evaluated at 1-2 wk, in 89% of those evaluated at 2-3 wk, and in 96% of those evaluated after 3 wk.
Conclusion: In most patients with thyroid cancer being prepared for (131)I imaging or therapy, a TSH level exceeding 30 micro IU/mL can be achieved by withdrawal of thyroid hormone therapy for 1-3 wk.