From the Research
Central diabetes insipidus is characterized by laboratory findings that include serum hyperosmolality, inappropriately dilute urine, elevated serum sodium, and low urine specific gravity, with a significant increase in urine osmolality after desmopressin administration, as noted in the most recent study 1. The typical lab findings for central diabetes insipidus include:
- Serum hyperosmolality (>295 mOsm/kg)
- Inappropriately dilute urine (urine osmolality <300 mOsm/kg)
- Elevated serum sodium (>145 mEq/L) due to free water loss
- Low urine specific gravity (<1.005), indicating very dilute urine
- Failure to concentrate urine during water deprivation testing, but a significant increase in urine osmolality (>50% increase) after administration of desmopressin (DDAVP), confirming ADH deficiency rather than kidney insensitivity to ADH, as seen in studies 2, 3, 4, 5. These findings occur because the posterior pituitary fails to release sufficient ADH, preventing water reabsorption in the collecting ducts of the kidneys, resulting in excessive water excretion despite the body's dehydrated state, as discussed in the literature 1. The diagnosis of central diabetes insipidus is based on a combination of clinical evaluation, measurement of urine and serum osmolality, and water deprivation test, with management including correction of any water deficit and the use of specific pharmacological agents, such as desmopressin, as recommended in the most recent study 1.