Endocrine Abstracts

Lithium increases retention of Iodine-131 in the thyroid gland and inhibits thyroid hormone release following radioactive iodine (RAI) administration. However, outcomes of studies of the effects of lithium on the efficacy of RAI are conflicting. The aim of this study was to assess whether adjuvant lithium increases the efficacy of RAI treatment in hyperthyroidism. A retrospective cohort study was performed of 204 hyperthyroid patients (163 Graves’ disease, 26 toxic multinodular goitre and 15 solitary toxic thyroid adenoma). 103 patients received RAI alone and 101 patients received RAI with adjuvant lithium (800 mg/d for ten days). The primary outcome measure was the proportion of patients cured at any time over a one year follow-up following RAI treatment. Secondary outcomes were thyroid hormone levels following RAI and incidence of thyroid eye disease following RAI. The likelihood of cure was approximately 50% greater in the RAI+lithium group at any time, even when adjusting for age, sex, cause of hyperthyroidism and dose of RAI. On completion of the one-year follow-up period, the cure rate for the RAI+lithium group was significantly greater than that of the RAI alone group (83.5% [RAI] vs 93.1% [RAI+lithium], P<0.05). There was a shorter time to cure (1.5 weeks) in the RAI+lithium group (P<0.05). Serum fT4 and fT3 were significantly lower in the RAI+lithium group compared to the RAI alone group (fT4: 12%, P<0.005, fT3: 17%, P<0.005). No deterioration in thyroid eye disease occurred in either group. This study supports the use of adjuvant lithium to improve the efficacy of RAI in the treatment of hyperthyroidism.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.