Final answer:
To differentiate central from nephrogenic diabetes insipidus, a water deprivation test and measuring urine osmolality and serum sodium levels are used. Central diabetes insipidus responds to ADH administration, while nephrogenic does not, as the kidneys are resistant to ADH effects. In contrast, diabetes mellitus involves high glucose levels in urine, leading to osmotic diuresis.
Step-by-step explanation:
To differentiate between central diabetes insipidus and nephrogenic diabetes insipidus, doctors utilize various diagnostic tests. Central diabetes insipidus is due to a deficiency of antidiuretic hormone (ADH) production or release from the brain, while nephrogenic diabetes insipidus is characterized by the kidney's resistance to the effects of ADH.
The water deprivation test is a common diagnostic tool where water intake is restricted, and urine output and osmolality are measured. In central diabetes insipidus, there is an increase in concentrated urine output after ADH (often as desmopressin) administration. Conversely, individuals with nephrogenic diabetes insipidus do not respond to ADH and continue to produce large volumes of dilute urine.
Urine osmolality and serum sodium levels are also commonly analyzed. In diabetes mellitus, urine will typically have high glucose levels resulting in an osmotic diuresis, where water is pulled into the urine due to high glucose concentrations leading to a larger urine output. In contrast, the urine in both forms of diabetes insipidus is dilute with a low osmolality compared to serum.