Sudden enlargement of local recurrent thyroid tumor after recombinant human TSH administration

Chronic endogenous TSH stimulation of neoplastic tissue has been reported t o stimulate tumor enlargement. However, little is known about changes in no rmal and neoplastic thyroid tissue after sudden rather than chronic stimula tion with TSH. Acute thyroidal tissue reactions, reflected by rapid tumor e xpansion and/or possible vascular changes, have been reported to occur afte r bovine TSH stimulation and, more recently, after recombinant human TSH (r hTSH). In this report, we describe two patients with papillary thyroid carcinoma w ith local recurrent tumor. Both patients developed tumor growth 12-48 h aft er the second rhTSH injection, reflected by acute respiratory distress or a palpable, tender mass. In both situations, the enlargement was documented by imaging techniques, showing tumor expansion compared with previous exami nations. Rapid improvement with glucocorticoid supports inflammation as the likely etiology. Based on these cases, and other reports of rapid tumor ex pansion after rhTSH injection, we recommend glucocorticoid coverage before rhTSH administration for patients with known or suspected neoplasia located in a limited space.