Treatment with 131I in differentiated thyroid carcinoma has been done with recombinant human TSH or suspending L-thyroxine for long time to arise TSH level to get good uptake of 131I. Both 131I treatment and follow- up require high stimulation of normal or pathological thyroid tissue remnants by TSH. We have evaluated the effectiveness of stimulation by multiple doses of TRH for radioiodine ablation of post surgical remnants stopping L-thyroxine at 3, 7 and 15 days protocol before injection of TRH and restarting L-thyroxine the day after the 131I.All patients underwent to total thyroidectomy.
The study includes three groups of patients: a group of 20 patients with differentiated thyroid carcinoma (15 papillary and 5 follicular stage I and II) using 100 mCi of 131I stopping L-T4 for one day and using 1 injection of TRH.
Group 2: with 25 patients with thyroid carcinoma (18 papillary and 7 follicular) at the same stage using 100 mCi of I-131 but stopping L-T4 for 3 days and using 2 injection of TRH.
Group 3: with 25 patients with thyroid cancer (20 papillary and 5 follicular) at the same stage using 100 mCi of 131I stopping L-T4 for 7 days and using three injection of TRH.
TSH reached a very good stimulation in the last two groups 40 -100 UI/l( mean 55±3) and(75-200 UI/l) mean 115± 6) The first group showed and increased of TSH level up to 60 UI/l (mean 42 ±3). All the patients showed thyroid remnants at WBS done 4-6 days after therapeutic dose administration.
Conclusion: It seems to be that multiple injections of TRH is a potent stimulator for TSH secretion that may induce 131I uptake by the normal or pathological remnant thyroid tissue. We know that using recombinant bovine or human thyrotropin (rh TSH) before radiotherapy increases TSH secretion and stimulates 131I uptake in thyroid remnants or in metastatic thyroid cancer. However, high price of these agents make inaccessible to the normal population who suffer this disease, therefore, thyrotropin-releasing-hormone (TRH) could be another possibility to stimulate own TSH secretion, but more studies to accomplish this approach it may be necessary.
This work was supported by the International Atomic Energy Agency.
