Area under the curve of TSH after levothyroxine withdrawal versus administration of recombinant human TSH (rhTSH): possible implications for tumor growth

OBJECTIVE: The levothyroxine withdrawal (L-T4) for some weeks results in prolonged exposure to elevated TSH. In contrast, administration of recombinant human TSH (rhTSH) promotes a short period of hyperthyrotropinemia. The objective of this study was to compare the area under the curve (AUC) of TSH obtained after L-T4 withdrawal versus administration of rhTSH. METHODS: Thirty patients received 0.9 mg rhTSH for two consecutive days, and 64 were prepared by L-T4 withdrawal for four weeks, with the latter being reintroduced 48 hour after 131I. Measurement of TSH were performed before the first rhTSH ampoule; immediately before and seven and 14 days after 131I; before L-T4 withdrawal; and, weekly, up to two months after 131I. RESULTS: The AUC obtained after rhTSH was 4.6 times smaller than that obtained after L-T4 withdrawal (532 versus 2,423 mIU/L per day). It should be emphasized that, on average, in the latter group, 58.5% of the AUC corresponded to the period after reintroduction of hormone therapy. CONCLUSIONS: Surprising difference in the TSH AUC was demonstrated between rhTSH administration versus L-T4 withdrawal.

Bibliographic Details

Main Authors:	Rosario,Pedro Weslley, Salles,Daniela Santos, Purisch,Saulo
Format:	Digital revista
Language:	English
Published:	Sociedade Brasileira de Endocrinologia e Metabologia 2009
Online Access:	http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0004-27302009000600012
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