Lithium as an adjunct to radioiodine therapy for thyrotoxicosis

16 patients with diffuse thyroid hyperplasia were given lithium carbonate (400 mg daily) for 1 week before and 1 week after a standardised 5 mCi therapy dose of 131I. A comparable control group of 16 patients were treated with 5 mCi of 131I without lithium therapy. The % retention of the therapy dose was measured in all patients at 7 days (168-hour 131I uptake). In the lithium-treated group the 24-hour 131I uptake showed no significant change after the first week of lithium therapy. The mean 48-hour protein-bound 131I, however, fell considerably from 1-21 to 0.55%/dose/1. The mean 24-168 hour % thyroidal 131I uptake drop was significantly less in the lithium group. These results show that low-dosage lithium therapy increases the retention of a standard-therapy dose of 131I. Lithium promises to be a useful adjunct to 131I therapy in patients with a rapid thyroidal iodine turnover and particularly in young patients where the total body-radiation dose must be kept to a minimum.