Diuretic use (especially loop and thiazide diuretics): These medications can lead to excessive sodium retention and potassium loss, resulting in hypernatremia and hypokalemia. The mechanism involves increased sodium reabsorption in the distal convoluted tubule and the loop of Henle, coupled with enhanced potassium excretion.

Hyperaldosteronism: Excess aldosterone promotes sodium retention and potassium excretion in the collecting duct, potentially leading to hypernatremia and hypokalemia. This condition can be primary (e.g., Conn's syndrome) or secondary (e.g., due to renal artery stenosis).
Cushing's syndrome: Glucocorticoids have a mild mineralocorticoid effect, which can cause sodium retention and potassium loss, especially at high levels. This can result in hypernatremia and hypokalemia.
Liddle's syndrome: A rare genetic disorder characterized by excessive sodium reabsorption and potassium secretion in the collecting duct, mimicking the effect of excessive aldosterone.

Adrenal crisis: Although less common, an adrenal crisis due to Addison's disease or other causes of adrenal insufficiency can present with hypernatremia and hypokalemia, among other electrolyte imbalances. Missing this diagnosis can be fatal.
Pheochromocytoma with paraganglioma: Rarely, these tumors can produce vasoactive substances that lead to hypertension and electrolyte disturbances, including hypernatremia and hypokalemia.

Bartter syndrome: A genetic disorder affecting the loop of Henle, leading to excessive sodium and potassium loss. However, in some cases, it might present with hypernatremia due to compensatory mechanisms.
Gitelman syndrome: Similar to Bartter syndrome but affecting the distal convoluted tubule. It typically presents with hypokalemia and hypomagnesemia but can have variable effects on sodium levels.
17α-Hydroxylase deficiency: A rare congenital adrenal hyperplasia that can lead to hypertension, hypokalemia, and sometimes hypernatremia due to the accumulation of mineralocorticoids.