Lithium as an adjunct to radioiodine therapy in Graves' disease for prolonging the intrathyroidal effective half-life of radioiodine. Useful or not?

AIM: Evaluation of intrathyroidal kinetics of radioiodine with and without lithium as adjunct with respect to the increase in radiation dose delivered to the thyroid. PATIENTS, METHODS: 267 patients in three groups were included in the study. Group I with 227 patients served as control group, Group II with 21 patients and Group III with 19 patients were distinguished by an intrathyroidal half-life of radioiodine below 3.5 days in the diagnostic test. Patients in Group III received 885 mg lithium carbonate a day for 2 weeks as adjunct to radioiodine therapy. Both diagnostic and therapeutic radioiodine kinetics were followed up by at least 10 uptake measurements within a minimum of 48 h. Kinetics of radioiodine were defined mathematically as balance of the thyroidal iodine intake and excretion by a two-compartment model. RESULTS: Under therapy the maximum uptake of radioiodine was reduced by nearly 10% in all groups, in Group I, the effective half-life as well as the product of maximum uptake x effective half-life as an equivalent of radiation dose independent of thyroid volume was lowered in the same magnitude. In Group II, the energy-dose equivalent remained constant under therapy. With adjunct lithium in Group III, the effective half-life was prolonged significantly by factor 1.61 +/- 0.49 and the volume-independent energy-dose equivalent by factor 1.39 +/- 0.37. No severe side effects of lithium were observed. CONCLUSION: Using lithium as adjunct to radioiodine therapy increases the radiation dose delivered to the thyroid by 39% on average and nearly 30% of radioiodine activity can be saved in these patients. Lithium is recommended in patients with very short effective half-life in the diagnostic test in order to reduce the activity required and whole-body radiation dose.

[Results of a risk adapted and functional radioiodine therapy in Graves' disease]. / Ergebnisse einer risikoadaptierten und funktionsorientierten Radioiodtherapie bei Morbus Basedow.

UNLABELLED: Aim of this study was to find out, if results of a functional orientated radioiodine therapy in Graves' disease could be optimized using a risk adopted dose concept. PATIENTS, METHOD: 351 patients with Graves' disease were treated for the first time between 11/97 and 8/01. The basic dose was 125 Gy, which was increased up to 250 Gy in a cumulative manner depending on clinical parameters (initial thyroid metabolism, thyroid volume, immunoreactivity). Two different methods of dosimetry were used. Occasional thyreostasis was withdrawn two days before the radioiodine test was started. Follow up was done on average 8 +/- 2.4 (4-17.2) months. TSH > or = 0.27 microIU/mL confirmed as a measure of the success. RESULTS: With improved pretherapeutic dosimetry and a mean target dose of 178 +/- 31 Gy (n=72) therapeutic success occurred in 66.7%, in 51.4% euthyreosis was restalled and in 15.3% of patients hypothyroidism was seen (TSH > 4.20 microIU/mL). With simplified pretherapeutic dosimetry and a mean target dose of 172 +/- 29 Gy (n=279) results were moderately impaired (63.8%, 40.1% and 23.7%). With increasing target dose therapeutic failure increased, as insufficiently adopted risk factors for therapeutic failure turned out the initial thyroid metabolism, the TcTU(s) as the (h)TRAb titer. CONCLUSION: Functional orientated RIT can be optimized by including illness specific characteristics, principal limitations are a high initial thyroid metabolism, a large thyroid volume and a high (h)TRAb-titer.