Acute lithium treatment suppresses the proestrous LH surge in mice: chronic lithium leads to constant diestrus.

Although the therapeutic usefulness of lithium in manic-depressive psychosis is now well-established, a number of basic and clinical studies in recent years have shown that the administration of this anti-manic drug produces a wide range of adverse endocrine and metabolic effects. The present study was undertaken in order to examine (a) what effects acute lithium administration might have on the preovulatory surge of luteinizing hormone (LH) during proestrus, and (b) whether chronic lithium administration has any adverse effect on the estrous cycle in C57BL/6 mice. Acute injections of lithium on the day of proestrus (at 10.00, 16.00 and 18.00 h; LD 14:10; lights on at 05.00 h CST) at a dosage of 5 mEq/kg b. wt. led to a significant (P less than 0.01) suppression of the LH surge that normally occurs in the evening of proestrus at 21.00 h. Chronic administration of lithium, on the other hand, resulted in a complete disruption in the regularity of the estrous cycle. This was characterized by an increasing number of mice showing a continuous diestrous vaginal smear during the first week of exposure to lithium, after which all of the lithium-treated mice completely stopped cycling and entered into constant diestrus. These results represent for the first time that lithium has significant adverse effects on the reproductive function in the female, especially in regard to the proestrous LH surge and estrous cyclicity in mice. Since these adverse effects were manifested under conditions when plasma lithium concentrations were within or around the therapeutic range, our results provide important conceptual information concerning possible adverse effects of lithium on the reproductive function in the human female.