Oral lithium as an adjunctive therapy during radioiodine treatment for hyperthyroidism

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We read with great interest the report by Basu and Abhyankar 1 on the use of a short course of oral lithium therapy as an adjunct in patients with thyrotoxicosis who failed initial radioiodine therapy (RAI). They reviewed studies on the subject from various settings revealing conflicting results of adjuvant lithium therapy during RAI for hyperthyroidism. Their report supports the use of adjunctive lithium in patients who have no contraindications to lithium use. That same group had previously reported a pilot study 2 in which they found that pretreatment with lithium was associated with a significantly reduced serum-free T4 level, especially in patients with diffuse toxic goitre.
In 2016, our group published the results of a prospective simple randomized comparative, experimental cohort study on adjuvant lithium during radioiodine treatment for hyperthyroidism 3,4. Unlike other studies where lithium was started days before RAI 5, in our South African study, daily administration of lithium carbonate (800 mg) began on the same day as the RAI dose, similar to that by Bal et al.6. However, unlike the study by Bal and colleagues, we administered lithium for a shorter period (7 days compared with 3 weeks). There was a good response to this therapy plan as evidenced by decrease in serum T4 and increase in thyroid-stimulating hormone levels in patients with Grave’s disease and toxic multinodular goitre as well as in both sexes 3,4. We showed that adjuvant lithium therapy increased the efficacy of radioactive iodine treatment in hyperthyroidism by increasing overall cure rate and shortening the time to cure. At 3 months after therapy, cure rates were significantly higher in patients who received RAI with adjuvant lithium compared with those who received RAI alone (78.4 vs. 56%). Thus, an additional 22.4% increase in cure rate was attributable to adjuvant lithium 3. The mean serum T4 concentration at 3 months was significantly lower in patients who received RAI with adjuvant lithium compared with those who received RAI alone. Although we were unable to measure serum lithium levels, no adverse effects were reported by participating patients.
In resource limited settings where RAI retreatment for hyperthyroidism may be hampered by long travel distances, high travel costs, and high attrition rates, our approach resulted in good cure rates. In patients requiring multiple treatments who may be at risk of loss to follow-up, we, like Basu et al. 1,2,5,7, believe that adjuvant lithium is safe and convenient during radioiodine treatment for hyperthyroidism in persons with no known contraindications to lithium and results in higher cure rates.

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