Endocrine Abstracts

Background: Radioactive Iodine (RAI) is one of the main treatment modalities of hyperthyroidism. Its success rate seems to differs. Lithium efficacy as adjuvant therapy to RAI remains debatable.

Objective: To assess the efficacy and safety of lithium carbonate as an adjuvant therapy to RAI in the treatment of hyperthyroidism.

Methods: This is 24 weeks prospective study carried out in the Endocrinology Unit, Penang General Hospital. Lithium carbonate 300 mg twice daily for fourteen days starting on the day of RAI therapy. Lithium carbonate 300 mg twice daily was given on the day of RAI (at least 2 h prior to RAI) to 40 subjects and no added medication in the control group. Subjects were followed up with 6 study visits to assess side-effects,compliance to medication, determining cure with adjustments to medications by the study doctors.

Results: There were no significant difference in the clinical, demographic and biochemical profile of the two groups. Dose of RAI standardized to 15 mCi in both groups. The cure rate in RAI plus lithium group was 62.2% vs 63.2% (P=0.932) in control. Mean time to cure in RAI plus Lithium versus RAI alone group were similar 13.6±6.1 weeks vs 13.2±6.5 weeks (P=0.841). There was numerically higher cure rate in Toxic Multinodular goitre in the RAI plus lithium group 10 out of 14 (71.3%) versus RAI alone group 8 out of 15 (53.3%)(P=0.316) though this was not statistically significant. Lithium however was able to prevent thyroid hormone surge 2 weeks post RAI as the median Free T4 was lower at week 2 post RAI compared to baseline (P=0.004).

Conclusion: Lithium carbonate does not improve the efficacy of RAI in hyperthyroid patients. Its role in improving efficacy of RAI in toxic multinodular goiter and prevention of thyroid hormone surge post RAI need further investigations.