Elevación insuficiente de TSH antes de la terapia con I131 en paciente con carcinoma diferenciado de tiroides metastásico

Guidelines suggest a thyrotropin (TSH) stimulation level ≥30 mIU/l for the administration of 131-iodine (I131) in patients with differentiated thyroid carcinoma (DTC). We present a patient with follicular thyroid carcinoma (FTC), with spinal metastasis as the initial manifestation, who after 6 weeks without levothyroxine did not present an elevation of ≥30 mIU/l of TSH. This situation was interpreted as secondary to the presence of functioning metastases and it was decided, regardless of the TSH level, to administer a therapeutic dose of I131, with iodine-uptake lesions in the liver and spine being confirmed.