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Children with Differentiated Thyroid Cancer Achieve Adequate Hyperthyrotropinemia within 14 Days of Levothyroxine Withdrawal

Division of Endocrinology, Children’s Hospital Boston, Boston, Massachusetts 02115

Address all correspondence and requests for reprints to: Dr. Stephen A. Huang, Harvard Institutes of Medicine, 77 Avenue Louis Pasteur, Room 642, Boston, Massachusetts 02115. E-mail: stephen.huang{at}childrens.harvard.edu.

Context: The preparation for radioiodine administration recommended by the current pediatric literature is a 6-wk withdrawal that typically includes the transient administration of T₃. Compared with adults, T₄ clearance rates and serum TSH to free T₄ ratios are higher in children, implying that pediatric patients can achieve adequate hyperthyrotropinemia with shorter levothyroxine withdrawals.

Objective: The objective of this study was to determine whether children with differentiated thyroid cancer achieve adequate hyperthyrotropinemia using an abbreviated levothyroxine withdrawal protocol.

Design: The study design was a retrospective analysis of 15 consecutive levothyroxine withdrawals performed without T₃ at Children’s Hospital Boston.

Patients: Eleven children with differentiated thyroid cancer were included. The average age at the time of withdrawal was 12.5 ± 0.8 yr.

Main Outcome Measurement: Serum TSH concentrations obtained after the discontinuation of levothyroxine were analyzed to determine the time interval required to achieve a serum TSH level greater than 25 µU/ml for each patient.

Results: Adequate hyperthyrotropinemia was documented in all children tested by d 14. The mean interval required to achieve a serum TSH level above 25 µU/ml from a suppressed serum TSH was 12.3 ± 0.7 d.

Conclusions: Shorter withdrawals minimize hypothyroid morbidity and the theoretical risk of decreased ¹³¹I residence time from excessive hyperthyrotropinemia. These benefits are amplified in children due to their high incidence of distant metastases. We propose an abbreviated 2-wk withdrawal protocol to facilitate the adjunctive therapy and surveillance of children with follicular cell-derived cancers.

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