Evaluation of lithium chronic effects on thyroid tissues and its secreted hormones in female rats

Lithium is an alkali metal element which has used in pharmaceutical compounds against diseases of psychopathy disorders, hypothyroidism and depression. This study was aimed to evaluate lithium chronic effects on thyroid tissues and its secreted hormones in female rats. In this experimental study, 48 female mature rats (Wistar race), were examined. Rats were divided in two random groups; each group had three subgroups in 8 rats. Lithium carbonate solution was injected to the experimental group, intraperitoneally every other day at 8 in the morning with the dosage of 180 mg/kg bodyweight of lithium carbonate saluted distillated water in during 40 days using insulin syringe, whereas the control group just injected distillated water. After 40 days, the rats were anesthetized and blood samples were taken from the left ventricle. Then, the thyroid gland was removed and after anatomical examination it was fixed in 10% formalin. Level of hormones in serum was evaluated by radioimmunoassay (RIA). The structure of the thyroid gland was examined by light microscopy. According to the results, there was a significant decrease in the thyroid weight of the experimental group (P=0.02), and thyrotropin (TSH) level decrease in the experimental group was significant as well (P=0.003). The level of thyroxine (T), T3 and T4 had a significant increase in the experimental group compared to control group (P=0.001). Regarding to the results, lithium carbonate has substantial effect on thyroid gland weight and on the serum levels of TSH, T3 and T4. Physicians should utilize this kind of medicine cautiously. Also it is recommended to warn patient about possibility of tyroidical disorder before treatment