Most common cause of hypernatremia
**Core Concept**
Hypernatremia is a condition characterized by an elevated serum sodium concentration, typically above 145 mmol/L. This imbalance can occur due to either excess sodium intake or water loss, leading to an increase in serum sodium levels.
**Why the Correct Answer is Right**
The most common cause of hypernatremia is **excessive water loss**, often resulting from diabetes insipidus (DI), a condition characterized by the inability to regulate water levels in the body due to a deficiency in antidiuretic hormone (ADH). This hormone plays a crucial role in regulating water reabsorption in the kidneys. When ADH levels are low, the kidneys are unable to properly reabsorb water, leading to excessive water loss through the urine. As a result, the body's water levels decrease, causing a relative increase in serum sodium concentration.
**Why Each Wrong Option is Incorrect**
* **Option A:** While excessive sodium intake can indeed lead to hypernatremia, it is not the most common cause. Excessive sodium intake typically results in a more rapid increase in serum sodium levels, whereas water loss is often a more insidious process.
* **Option B:** Hypertonic saline administration can cause hypernatremia, but it is not a common cause in clinical practice. This option is more relevant to medical emergencies where hypertonic saline is used to rapidly correct severe hyponatremia.
* **Option C:** Congestive heart failure (CHF) can lead to fluid overload, which may result in hyponatremia rather than hypernatremia. While CHF can cause electrolyte imbalances, it is not typically associated with hypernatremia.
**Clinical Pearl / High-Yield Fact**
Remember that hypernatremia often presents with symptoms of dehydration, such as dry mouth, dark urine, and decreased urine output. In contrast, hyponatremia may present with symptoms of water intoxication, such as confusion, seizures, and headache.
**Correct Answer:** C.