Initially high plasma prolactin levels are depressed by prolonged psychological stress in males

Plasma levels of prolactin were determined by radioimmunoassay in medical students before and after an academic examination and corresponding control periods. Before the academic examination, both the males' and the females' prolactin values were higher than their control values; they were statistically significant, however, only in the males. After the examination, the prolactin values were lower than the control values in the males, but not in the females. The results partly explain the diverging opinions in the literature regarding the effect of psychological stress on plasma prolactin.