Effect of Lithium on Thyroid Function

Abstract

Thyroid function was evaluated before and during lithium carbonate therapy in 13 patients. One patient developed a goiter which subsided with desiccated thyroid; another patient, already on lithium, had a goiter which markedly decreased in size when the drug was discontinued. The administration of lithium to 2 thyrotoxic patients resulted in an acute inhibition of the discharge rate of 131I− from the thyroid gland. The short-term administration of lithium to rats whose thyroid glands were subsequently labeled with 131I− resulted in a decrease in the per cent distribution of radioactive thyroxine by chromatography in lithium-treated as compared to control animals. Lithium had no effect on the 131I− thyroid/serum ratio or iodotyrosine formation. The lithium concentration in pooled rat thyroid glands was 10.1 mEq/kg compared to a mean serum level of 1.9±0.6 mEq/1. Despite certain inhibitory effects of lithium, the basic mechanism for the goitrogenic effect of this cation is still unclear.