In the levodopa-stimulation group, the maximum value of copeptin in patients with AVP deficiency was significantly lower than that in non-AVP deficiency patients (<i>p</i>=0.000 2), and the area under the receiver operating characteristic curve was 0.98 (95% confidence interval 0.94-1.00, <i>p</i>=0.002 1). The gene discussed is AVP; the disease is neurohypophyseal diabetes insipidus.