Choose the best Lab value for a patient with central diabetes insipidus
Diabetes insipidus is the reverse of SIADH, here the ADH level is decreased which leads to excessive water loss from the kidney resulting in hypertonic plasma associated with dilute urine.
It can be

- Central     → (due to impaired secretion of ADH from the neurohypophysis)
- Nephrogenic →   (due to renal insensitivity or nonresponsiveness to ADH).

In both circumstances. the serum osnzolality is increased with inappropriately low urine osmolalitv.
The two may be distinguished, however, by the response to either exogenous or endogenous vasopressin.
In neurogenic (central) DI,

- ADH levels are 100, and the kidney rapidly acts to conserve water once exogenous ADH is administered.

In contrast, in nephrogenic DI,

- ADH is associated with normal or increased ADHe levels and administration of additional ADH has no significant effect on renal water reabsorption.
Also known
Urinary Osmolality - 50, Serum Osmolality - 300
Urinary Osmolality - 500, Serum Osmolality - 260
Urinary Osmolality - 50, Serum Osmolality - 260
Urinary Osmolality - 500, Serum Osmolality - 100