Which condition is NOT a common cause of hypernatremia?

Hypernatremia, which is characterized by elevated sodium levels in the blood, commonly arises from conditions that lead to a loss of water relative to sodium in the body. Dehydration involves the loss of fluids, leading to increased concentration of sodium. Diabetes insipidus results in excessive urination and loss of water that can raise sodium levels as well. Cushing's disease causes increased cortisol levels, which can also contribute to sodium retention and hypernatremia.

In contrast, the syndrome of inappropriate ADH secretion (SIADH) is characterized by excessive release of antidiuretic hormone (ADH), which leads to water retention and dilution of sodium in the bloodstream. This results in hyponatremia, rather than hypernatremia, making SIADH the condition that does not typically cause elevated sodium levels.