Complex antithyroid properties of the lithium ion. A study in rats
Männistö, P.T.; Leppäluoto, J.; Virkkunen, P.
Acta Endocrinologica 74(3): 492-500
1973
ISSN/ISBN: 0001-5598 PMID: 4800849 Document Number: 58001
The test animals were male Sprague-Dawley rats, weighing 190 to 210 g, in groups of 7. Diet was either of normal I content, 0.6 to 1.0 mg/kg, or low in I, 0.03 to 0.05 mg/kg, to which the animals were accustomed for 2 weeks before the test. The normally fed test rats were given at 0, 12 and 20 h in the first day LiCl 5 m-equiv/kg bodyweight; the low-I test rats 2.5, 5.0 or 7.5 m-equiv/kg by intraperitoneal injection in normal saline. With the last dose of each 25 mu Ci 131I was injected. For comparison other groups on normal diet had RbCl 5 m-equiv/kg, or carbimazole 0.05 m-equiv/kg; or were subjected to 30 min stress by handling. At death one lobe of each thyroid, after 4 h hydrolysis with pronase, was examined by paper chromatography or electrophoresis. Plasma thyroid stimulating hormone (TSH) was estimated by radioimmunoassay, plasma corticosterone by fluorimeter, plasma Li by flame photometer, and plasma 131I and the thyroid tyrosines and thyronines (MIT, DIT, T3 and T4) with a gas-flow 4-pi tube. In the rats on normal diet LiCl, RbCl and carbimazole reduced the 4-h uptake of 131I by the thyroid and LiCl and carbimazole reduced synthesis of T3 and T4. Plasma TSH was slightly reduced by Li and Rb and by stress, but increased by carbimazole. In the test with low-I diet 4-h uptake of 131I fell as the intake of Li rose and synthesis of T4, T3, DIT and finally MIT also fell; iodide was not affected. Plasma corticosterone rose and TSH fell as plasma Li rose. Hence it is suggested that massive doses of Li could be goitrogenic.