Arquivos Brasileiros de Endocrinologia & Metabologia
On-line version ISSN 1677-9487
ROSARIO, Pedro Weslley; SALLES, Daniela Santos and PURISCH, Saulo. Area under the curve of TSH after levothyroxine withdrawal versus administration of recombinant human TSH (rhTSH): possible implications for tumor growth. Arq Bras Endocrinol Metab [online]. 2009, vol.53, n.6, pp.767-770. ISSN 1677-9487. http://dx.doi.org/10.1590/S0004-27302009000600012.
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.
Keywords : Thyroid neoplasms; tumor growth; recombinant human TSH.