Does lithium administered with radioiodine therapy improve the cure rate for thyrotoxicosis?
GMK Nijher, S Skennerton & K Meeran
Radioactive iodine (RAI) is a well-established treatment for relapsed Graves and toxic nodular hyperthyroidism. Lithium reduces the release of organic iodide and thyroid hormones from the thyroid gland, which results in a reduction of urinary radioiodine excretion. Previous studies have shown lithium may improve the effectiveness of radioiodine therapy; however research in this area is limited.
To study the efficacy of radioiodine therapy alone and radioiodine combined with lithium for treatment of hyperthyroidism to render the patient euthyroid or hypothyroid.
59 patients with hyperthyroidism were randomly assigned to treatment with either RAI alone or RAI with lithium and evaluated for changes in thyroid function 9 days before and 1, 3, 9, 12 weeks after treatment. Urinary Iodine excretion measurements from 24-hour urine collections were obtained at 9 days prior to and on the day of RAI therapy. Local committee ethics approval was obtained.
89% of the patients on RAI with lithium and 100% of the patients on RAI alone were cured, P=0.71. Patients on RAI and lithium excreted more iodine 118.7±143.4 nmol/mmol compared to those on placebo 82.5±64.1 nmol/mmol; however this difference was not significant P=0.03. Patients on lithium took less time 7.3±8.0 weeks to become hypothyroid than those on placebo 8.8±6.2 weeks, although this difference did not reach significance P=0.229. Males took significantly longer to become cured 10.3±9.1 weeks than females 7.0±6.7 weeks P=0.03.
Lithium does not appear to improve the efficacy of RAI and hence does not improve the rate of patient cure post radioiodine. This may be as a result of the excellent cure rate achieved in both groups during this trial. A larger number of patients is necessary to demonstrate a significant difference in outcome of patients with lithium.