Treatment With Lithium Prevents Serum Thyroid Hormone Increase After Thionamide Withdrawal and Radioiodine Therapy in Patients With Graves disease

摘要

Background: Antithyroid drugs (ATD) are frequently given for a few months before ~131I therapy, primarily to reduce the degree of thyroid hormone rise after the administration of ~131I. Propyl-thiouracil pretreatment is associated with a higher failure rate of ~131I therapy, whereas methimazole (MMI) does not affect the cure rate (Thyroid 2002; 12: 131). There is controversy about the origin of the transient rise in serum thyroid hormone that occurs after ATD withdrawal and ~131I treatment of thy-rotoxic Graves disease. Whether it is caused by withdrawal of ATD or is caused by ~131I-induced disruption of the follicular cells has been a matter of debate.Materials and Results: This prospective, randomized, blinded study addresses these questions and explores the use of lithium as an adjunct to ~131I treatment of thyrotoxicosis. The study confirms that MMI withdrawal causes a prompt rise in serum free T4 and free T3 concentrations within 2 days, approaching a plateau within 5 days that can be prevented by lithium. Furthermore, ~131I therapy produced a further increment in serum free T4 levels on day 1 after ~131I that peaked on day 5, whereas patients treated with lithium had a slight rise in serum thyroid hormone levels on day 1, with a rapid decline in the next 3 to 5 days. The abrupt rise in serum thyroid hormone levels in all study groups on the first day after ~131I therapy suggests that it is caused by discharge of preformed thyroid hormone from ~131I-induced lysis of thyroid follicular cells. Although the therapeutic dose of ~131I did not differ in the three treatment groups, the two lithium-treated groups retained ~131I longer than the group not so treated, as would be expected, and thus received a significantly higher absorbed dose of ~131I. Cure of hyperthy-roidism occurred in 67% of the group not treated with lithium and in 92% in each of the lithium-treated groups.Comment: The authors advise giving a short course of lithium as an adjunct to ~131I therapy, which provides prompter control of thyrotoxicosis and avoids the transient exacerbation of symptoms accompanying MMI withdrawal and ~131I administration. The fact that serum thyroid hormone concentrations after ~131I did not differ in the two lithium-treated groups suggests that lithium could be withdrawn 1 week after ~131I administration. No adverse effects were noticed from lithium except for a slightly higher (but not statistically significant) incidence of nausea and neck tenderness in the group receiving lithium for 19 days. Lithium has been used for longer than a week in hypothyroid patients with thyroid cancer being treated with ~131I, without producing adverse effects. The observations offer a new and effective paradigm in the ~131I treatment of thyrotoxicosis. (EM)