CHGA and neuroendocrine neoplasm: There was also a correlation between the concentration of chromogranin A and the concentrations of other markers of neuroendocrine neoplasms, such as serotonin and 5-hydroxyindole acetic acid (rS = 0.38 and p < 0.05 and rS = 0.33 and p < 0.05, respectively) and between serotonin and 5-hydroxyindole acetic acid (rS = 0.4, p < 0.05).