Background: Patients with thyroid cancer often need whole-body scintigraphy (WBS) under TSH stimulation after 4-6 weeks withdrawal from levothyroxine (L-T(4)). Patients often become severely hypothyroid with impaired quality of life. Liothyronine (L-T(3)) substitution is used empirically to prepare patients; however, no data exist to prove its benefit. Objectives To compare the hypothyroid state in patients receiving either placebo or L-T(3) following L-T(4) withdrawal and to evaluate the time needed for adequate TSH elevation in preparation for WBS.
Methods: At the time of L-T(4) withdrawal, patients were randomized to receive L-T(3 )(50 microg qd) or placebo for 3 weeks, after which treatment was stopped. A validated evaluation of hypothyroidism (Billewicz score) was administered in a double-blind fashion every 2 weeks until the WBS. TSH, fT(4) and fT(3) were measured weekly.
Results: A total of 20 patients were randomized between September 2003 and May 2005. There was no difference in the Billewicz score at any time between the two groups. Before WBS, both groups were profoundly hypothyroid. TSH at time of WBS was similar in both groups. The time needed to reach a TSH level of more than 30 mUI/l was longer in L-T(3) group (mean +/- SD: 32 +/- 4 days vs. 17 +/- 9 days in placebo group, P = 0.006).
Conclusion: Preparation for WBS with L-T(3) does not prevent profound hypothyroidism and delays TSH elevation required for WBS. L-T(4) withdrawal alone for 2-3 weeks is simpler and sufficient to allow TSH to reach a level of more than 30 mUI/l in the majority of patients without increasing morbidity from hypothyroidism.