The Significance of Plasma ADH in Differential Diagnosis of Central Diabetes Insipidus / 대한내분비학회지

ABSTRACT

BACKGROUND: Although the water restriction test(WRT) has been used as a standard test for the differential diagnosis of diabetes insipidus(DI), the measurement of plasma ADH concentration is also known to be useful method for differential diagnosis. Recent studies have shown that some patients with idiopathic central DI(CDI) were found to have a lesion on follow-up imaging studies. There have been no report in Korea on plasma ADH measurement for the differential diagnosis of DI, nor on follow-up imaging study of the idiopathic CDI. METHODS: We retrospectively reviewed the clinical and laboratory findings of 26 patients(12 men, 14 women, age 9-65 years) with CDI, including pituitary MRI or CT scan, who had been diagnosed with WRT and had undergone plasma ADH concentration measurement. RESULTS: 1) Clinical features of the patients with complete CDI did not differ from those of patients with partial CDI. 2) Maximal urine osmolality of complete CDI and partial CDI were 168+/-69mOsm/kg and 431+/-141mOsm/kg, respectively, and the percentage increase in the urinary osmolality after ADH injection was 209+/-149% and 29+/-17%, respectively. 3) Among the 26 patients, 10 patients had their plasma ADH measured. Nine patients in this group were diagnosed as CDI by WRT and plasma ADH concentration of the 9 was compatible for CDI. The plasma ADH level was also inappropriately low in one patient who had been diagnosed with primary polydipsia by WRT, the patient was diagnosed as partial CDI. 4) The findings of follow-up MRI revealed isolated thickening of the pituitary stalk in two cases of idiopathic CDI diagnosed initially with MRI. CONCLUSION: This study suggests that the measurement of plasma ADH can ensure a better differential diagnosis between partial CDI and primary polydipsia, and that the patients with idiopathic CDI should be examined regularly with MRI brain scan, including the pituitary gland.