A Pregnant Woman with Excess Vasopressinase-Induced Diabetes Insipidus Complicated by Central Diabetes Insipidus like Lymphocytic Infundibulo-Neurohypophysitis

Figure 3

Result of the hypertonic saline infusion test. The relationship between plasma arginine vasopressin (AVP) and serum sodium levels in a 5% hypertonic saline infusion test was performed at four weeks postpartum. Plasma AVP levels did not sufficiently increase in response to the gradual increase in serum sodium levels. Simple linear regression analysis revealed that the equation of the regression line was Y = 0.025X − 2.9. The slope (=0.025) was <0.1, and the estimated plasma AVP level (=0.825 pg/mL) at a serum sodium level of 149 mEq/mL was <1.0 pg/mL, thus fulfilling the diagnosis criteria for central diabetes insipidus. For reference, the normal range of plasma AVP levels based on the data measured by a former AVP-radioimmunoassay (RIA) kit (Mitsubishi Petrochemical Co. Ltd., Tokyo, Japan), which is now unavailable in Japan, is shown. It is reported that plasma AVP levels measured by the Yamasa RIA kit are significantly and positively correlated with those measured by the Mitsubishi RIA kit (Spearman’s rank correlation coefficient (r) = 0.905, ) [9, 10].