Transient Vasopressin-Resistant Diabetes Insipidus of Pregnancy

OSMOREGULATION is markedly altered in normal human pregnancy. Osmotic thresholds for both thirst and secretion of arginine vasopressin decrease, and plasma osmolality and sodium levels are reduced by 10 mOsm per kilogram and 4 mmol per liter, respectively, as compared with levels measured before pregnancy.1 2 3 Despite this lower osmolality, pregnant women maintain basal levels of plasma arginine vasopressin of 1 to 2 pg per milliliter — values similar to those of nongravid subjects — and concentrate their urine appropriately when they are dehydrated.3 , 4 This is all the more intriguing since two developments during normal gestation would be expected to interfere . . .