Excessive dopaminergic activity in some dopaminergic tracts may be involved in the cause of some types of schizophrenia. We studied serum prolactin levels in newly admitted, unmedicated, psychiatric patients to determine if the prolactin levels in schizophrenic patients might be diminished to reflect increased dopaminergic activity in the tuberoinfundibular tract or the increases associated with psychological stress. Mean serum prolactin concentration was found to be within the normal range in 22 unmedicated, acutely disturbed, newly admitted schizophrenic patients but tended to be elevated in two manic patients and one patient with a severe anxiety state.
It may be possible to use these findings to assess the degree of dopaminergic activity of the tuberoinfundibular tract. It appears that the mechanism that causes stress to increase serum prolactin may be abnormal in some schizophrenic patients.