of diabetes insipidus can also be hereditary due to defects in the following genes: Diagnosis Differential diagnosis includes nephrogenic diabetes insipidus, neurogenic/central diabetes insipidus and psychogenic polydipsia. They may be differentiated by using the water deprivation test. Recently, lab assays for antidiuretic hormone are available and can aid in diagnosis. If able to rehydrate properly, sodium concentration should be nearer to the maximum of the normal range. This, however, is not a diagnostic finding, as it depends on patient hydration. Desmopressin can also be used; if the patient is able to concentrate urine following administration of desmopressin, then the cause of the diabetes insipidus is neurogenic diabetes insipidus; if no response occurs to desmopressin, then the cause is likely to be nephrogenic. Treatment Persons with nephrogenic diabetes insipidus will need to consume enough fluids to equal the amount of urine produced. Any underlying cause such as high blood calcium must be corrected to treat nephrogenic diabetes insipidus. The first line of treatment is hydrochlorothiazide and amiloride. Patients may also consider a low-salt and low-protein diet. Thiazide diuretics are used in treatment because diabetes insipidus causes the excretion of more sodium than water, while maintaining the corticomedullary gradient (not maintained when using loop diuretics). The maintained corticomedullary gradient allows more absorption of water in the collecting duct. This improves the blood osmolarity and prevents hypernatremia. High serum osmolarity stimulates polydipsia in an attempt to dilute the serum back to normal and provide free water for excreting the excess serum solutes. However, since the patient is unable to concentrate urine to excrete the excess solutes, the resulting urine fails to decrease serum osmolarity and the cycle repeats itself, hence polyuria. Etymology The name of the disease comes from: diabetes: from , from diabḗtēs "a passer-through; siphon", from Greek διαβαίνειν diabaínein "to pass through", from δια- dia- "through" + βαίνειν baínein "to go". insipidus: from Late Latin: insipidus "tasteless," from Latin in- "not" + sapidus "tasty", from sapere "to taste". This is because patients experience polyuria (an excretion of over 2.5 liters of urine per day), and the urine does not have an elevated glucose concentration, as opposed to diabetes mellitus. The two diseases were named (in ancient times) for the fact that one features polyuria in which the urine tastes sweet, whereas the other features polyuria in which the urine tastes unremarkable. Although they share part of their names, diabetes mellitus and