Which hormone is involved in regulating water balance in the body?

• A. Estrogen
• B. Adrenaline
• C. Antidiuretic hormone (ADH)
• D. Insulin

Answer: (C)

Antidiuretic hormone (ADH), also known as vasopressin, plays a crucial role in regulating water balance in the body. It is produced in the hypothalamus and released from the posterior pituitary gland in response to elevated blood osmolarity or decreased blood volume. ADH acts primarily on the kidneys, where it increases the permeability of the renal collecting ducts to water. This action promotes the reabsorption of water back into the bloodstream, which helps to concentrate urine and reduce water loss from the body. By increasing the retention of water, ADH effectively helps maintain proper hydration levels and blood pressure, illustrating its essential role in water balance regulation.

The other hormones listed do not primarily function in this capacity. Estrogen is mainly involved in reproductive functions and secondary sexual characteristics, while adrenaline is associated with the body's fight-or-flight response and affects heart rate and blood flow. Insulin primarily regulates glucose metabolism and plays a central role in maintaining blood sugar levels. Thus, ADH stands out as the specific hormone tasked with managing the body's water balance.