R040

Lithium is a useful adjuvant in patients receiving radioactive iodine for hyperthyroidism

Miraj Patel¹, Gurjinder MK Nijher^1,2, Shivani Misra^1,2, Elaine Murphy¹, Karim Meeran^1,2 and Niamh M Martin^1,2

1  Section of Investigative Medicine, Imperial College, London, W12 0NN

2 Imperial Centre for Endocrinology

Abstract:

Context

Lithium increases ¹³¹I retention within the thyroid gland and inhibits thyroid hormone release following radioactive iodine (RAI) administration. However, studies of the effects of adjuvant lithium on RAI treatment are conflicting.

Objective

To assess whether adjuvant lithium increases the efficacy of RAI treatment in hyperthyroidism.

Design and setting

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 (800mg/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.

Results

Cure of hyperthyroidism was 50% more likely in the RAI + lithium group at any time, even when adjusting for age, sex, cause of hyperthyroidism and dose of RAI. At one year post-RAI, 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). Time taken to achieve cure was 1.5 weeks shorter 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). There was no deterioration in thyroid eye disease in either group.

Conclusion

This study supports the use of adjuvant lithium to improve the efficacy of RAI in the treatment of hyperthyroidism.