Diabetes insipidus and SIADH are endocrine disorders that cause electrolyte imbalances. Diabetes insipidus is caused by a lack of antidiuretic hormone leading to excessive urine output and thirst. SIADH is caused by inappropriate antidiuretic hormone secretion leading to water retention and hyponatremia. Both require fluid management through oral or IV rehydration and medication to regulate antidiuretic hormone levels. Nurses monitor electrolytes, fluid intake and output, and symptoms like thirst, nausea, or edema.