Which hormone regulates water balance in the body?

The hormone that regulates water balance in the body is antidiuretic hormone (ADH), also known as vasopressin. ADH is produced in the hypothalamus and released from the posterior pituitary gland. Its primary function is to control the amount of water reabsorbed by the kidneys. When the body is dehydrated or when blood osmolality is high, ADH levels increase, prompting the kidneys to reabsorb more water back into the bloodstream and reduce urine output. This mechanism helps maintain proper water balance and electrolyte concentrations in the body, thereby playing a crucial role in homeostasis.

In contrast, adrenaline is primarily involved in the body's fight-or-flight response, enhancing energy availability and increasing heart rate, while cortisol is a stress hormone that regulates a range of functions, including metabolism and immune response. Insulin is essential for regulating blood sugar levels and does not directly influence water balance. Understanding the specific roles of these hormones helps clarify why ADH is the key regulator of water balance in the body.