Abstract
Radioiodine therapy (131I) is a standard procedure in the treatment of hyperthyroidism in the course of Graves' disease or toxic nodules. However, the use of 131I in patients with low radioiodine uptake (RAIU) may be controversial. To determine the influence of lithium carbonate (Li) on iodine kinetics. Patients with hyperthyroidism and low RAIU (< 30%) were divided into 2 groups: a Li(-) group of 305 patients not receiving Li adjuvant therapy and a Li(+) group of 264 patients receiving adjuvant therapy. The serum concentrations of free triiodothyronine (fT3), free thyroxine (fT4) and thyroid stimulating hormone (TSH) were assessed at baseline, 24 h, 48 h, 72 h and 96 h, and 1, 6 and 12 months after 131I therapy. The RAIU was assessed after 5 h, 24 h, 48 h, 72 h, and 96 h. Levels of fT3 in the Li(+) group compared to the Li(-) group were significantly higher at baseline, lower after 48 h, 72 h, 96 h and 1 month, and did not differ significantly after 24 h, 6 months and 12 months. Levels of fT4 in the Li(+) group compared to the Li(-) group were significantly higher at baseline, lower after 24 h, 48 h, 72 h, 96 h and 1 month, and not differ significantly after 6 and 12 months. The RAIU in the hyperthyroidism Li(-) and Li(+) groups, respectively, was 11.9 ±5.6% compared to 23.9 ±10.1% (p < 0.001) after 5 h; 25.9 ±8.3% compared to 40.5 ±12.4% (p < 0.05) after 24 h; 7.8 ±8.1% compared to 40.9 ±13.7% (p < 0.05) after 48 h; 26.2 ±10.2% compared to 39.5 ±11.2% (p < 0.01) after 72 h; and 24.7 ±7.1% compared to 37.4 ±10.1% (p < 0.01) after 96 h. Adjuvant therapy with Li in patients with hyperthyroidism caused a significant increase in RAIU and positive changes in the fT3 and fT4 profiles. The use of lithium carbonate prior to the inclusion of 131I in hyperthyroid patients with low RAIU should be considered.
Highlights
Radioiodine therapy (131I) is a standard procedure in the treatment of hyperthyroidism in the course of Graves’ disease or toxic nodules
Levels of free T3 (fT3) in the lithium carbonate (Li)(+) group compared to the Li(−) group were significantly higher at baseline, lower after 48 h, 72 h, 96 h and 1 month, and did not differ significantly after 24 h, 6 months and 12 months
The radioiodine uptake (RAIU) in the hyperthyroidism Li(−) and Li(+) groups, respectively, was 11.9 ±5.6% compared to 23.9 ±10.1% (p < 0.001) after 5 h; 25.9 ±8.3% compared to 40.5 ±12.4% (p < 0.05) after 24 h; 7.8 ±8.1% compared to 40.9 ±13.7% (p < 0.05) after 48 h; 26.2 ±10.2% compared to 39.5 ±11.2% (p < 0.01) after 72 h; and 24.7 ±7.1% compared to 37.4 ±10.1% (p < 0.01) after 96 h
Summary
Radioiodine therapy (131I) is a standard procedure in the treatment of hyperthyroidism in the course of Graves’ disease or toxic nodules. Various studies have shown that it can cause the emergence of goiter and even hypothyroidism in the range of 3.4–52% of treated patients[1,2,3,4,5,6,7,8,9] and, in extremely rare cases, hyperthyroidism.[1,10,11] The mechanism of action of Li on thyroid function seems to be similar to that of iodine. It is believed that ionized lithium inhibits thyroglobulin proteolysis which, in turn, inhibits the release of thyroid hormones into the bloodstream and leads to a prolonged biological half-life of iodine.[12] Another mechanism involves inhibition of the conversion of free thyroxine (T4) to triiodothyronine (T3) by this drug.[1] Lithium carbonate has been shown to reduce the concentration of thyroid hormone transporter proteins in the blood serum.[1,13]
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