The effects of lithium on neuroendocrine function in affectively ill patients.

Lithium is the primary treatment for manic-depressive illness. The mechanism of action of lithium and its endocrine effects remain unclear. Therefore, the hormone responses to sequential stimuli, namely arginine, TRH, and LHRH, were studied in eight patients with major depression before and during treatment with lithium. The drug was found to elevate baseline TSH and prolactin and to augment both their responses to TRH. No clinically significant effect on sex hormones was noted. The advantages of the experimental design and the implications of the findings for lithium's mechanism of action are discussed.