AEMCA Practice Exam

Which hormone is responsible for the regulation of water balance in the body?

1. Vasopressin

2. Thyroxine

3. Insulin

4. Testosterone

The correct answer is: Vasopressin

Vasopressin, also known as antidiuretic hormone (ADH), plays a critical role in regulating water balance in the body. It is secreted by the posterior pituitary gland and is primarily involved in controlling the amount of water reabsorbed by the kidneys. When the body is dehydrated or experiences high osmolarity (concentration of solutes in the blood), vasopressin is released into the bloodstream. This hormone acts on the renal tubules, increasing their permeability to water, thereby promoting water reabsorption back into the bloodstream and reducing water loss through urine. This mechanism is essential for maintaining homeostasis, ensuring that body fluids remain balanced and preventing conditions such as dehydration or overhydration. In contrast, the other hormones listed serve different functions: thyroxine is responsible for regulating metabolism, insulin primarily regulates blood sugar levels, and testosterone plays a key role in sexual development and reproductive function. None of these hormones directly influence water balance in the same way that vasopressin does.