Growth hormone levels and lithium ratios as predictors of success of lithium therapy in schizophrenia

The authors previously found a high correlation between lithium response and clinical diagnostic criteria in a subgroup of schizophrenic-like patients who responded favorably to lithium therapy. In the present study the authors extend this research by using biological markers to predict and identify such patients. They examined growth hormone (GH) response to apomorphine administration and the in vitro lithium ratio in 31 patients before and after a 2-week lithium trial. Peak GH levels (greater than or equal to 20 ng/ml) and lithium ratios (greater than or equal to .39) were correlated with a positive response to lithium therapy. The authors discuss 1) the use of these two biological markers to predict the success of lithium therapy in schizophrenia and 2) biological abnormalities characteristic of lithium- responsive schizophrenic patients.