APPLICATION: ADH measurement is only useful in the context of a water deprivation test to diagnose diabetes insipidus or in some cases of suspected SIADH. In diabetes insipidus the test may be used, in conjunction with plasma osmolality, to distinguish between central and nephrogenic diabetes insipidus. Random ADH levels are not interpretable.
INTERPRETATION: Central diabetes insipidus is associated with low antidiuretic hormone (ADH) levels when plasma osmolality is elevated. Nephrogenic diabetes insipidus is associated with increasing levels of ADH as plasma osmolality increases.
