After the removal of the thyroid gland (thyroidectomy) thyroid hormones have to be substituted to attain a normal way of life. Thyroid hormone withdrawal for four to six weeks has been used for more than 50 years for the treatment of metastatic differentiated thyroid cancer after thyroidectomy because residual cancer cells may then be better destroyed by radiation therapy using radioiodine. Another therapeutic approach to prepare for radiation uses injections of technologically created (recombinant) human thyroid-stimulating hormone (thyrotropin, TSH) to avoid the symptoms of a malfunctioning thyroid gland (hypothyroidism), which are caused by thyroid hormone withdrawal. This technique has been approved for use in the diagnosis of recurrent and metastatic differentiated thyroid cancer and in the preparation of patients for elimination of normal thyroid remnants after thyroid surgery, but not for treatment of known locally recurrent or metastatic disease.
Overall 223 patients with differentiated thyroid cancer participated in four studies. The duration of the intervention (injections of recombinant human thyrotropin) was two days in all trials. Studies were of rather low quality. We found no statistically significant differences between recombinant human thyrotropin and thyroid hormone withdrawal treatment in terms of successful reduction of thyroid remnants or cancer cells but significant benefits in radiation exposure to blood and bone marrow. One trial reported on benefits in some domains of health-related quality of life. There were no deaths and no serious adverse effects observed, however maximum follow up was only 12 months. None of the included trials investigated complete or partial remission of metastatic tumour, secondary malignancies or economic outcomes. We did not find sufficient data comparing recombinant human thyrotropin with thyroid hormone withdrawal-aided radioiodine treatment for metastatic differentiated cancer.