Lithium effects on neuroendocrine function

We studied growth hormone and prolactin responses to insulin hypoglycemia and TSH response to TRH in symptom-free bipolar patients and healthy controls. There were no significant differences in prolactin and growth hormone responses to hypoglycemia between stabilized bipolar patients and healthy controls, both tested medication-free. When lithium was administered to both groups, only bipolar patients showed a dramatic reduction in prolactin and growth hormone responses. Both bipolar patients in remission and healthy controls showed an increase of TSH response to TRH when treated with lithium in comparison with the testings before lithium administration. The subjects, both patients and volunteers, showed a comparable degree of hypoglycemia on and off lithium. The observed difference in responsiveness of bipolar patients warrants further systematic investigation and offers interesting possibilities for practical utilization.