Circulating nitric oxide is modulated by recombinant human TSH administration during monitoring of thyroid cancer remnant

During the administration of recombinant human TSH (rhTSH) to monitor differentiated thyroid carcinoma, mild side effects, such as nausea and headaches, often occur. The origin of these is not clear. Since changes in TSH and thyroid hormones can modulate some endothelial-derived factors, we aimed at testing whether rhTSH administration induces changes in nitric oxide. We studied 25 patients (56.6+/-12.6 yr) who had undergone thyroidectomy followed by ablative radioiodine for papillary thyroid cancer and who were under follow-up. While L-thyroxine therapy continued, thyroglobulin (Tg), TSH, free-T3, free-T4 and nitrite-plus-nitrate (NOx) concentrations were evaluated before and after rhTSH administration (0.9 mg i.m. on 2 consecutive days). Mean TSH showed a huge increase from baseline (0.1+/-0.0 mIU/l) to day 3 (216.3+/-17.5 mIU/l, p