ATI Pathophysiology Practice Exam

What happens to body fluid when antidiuretic hormone is secreted?

1. Increased excretion of water

2. Decreased blood volume

3. Increased retention of water

4. Decreased electrolyte concentration

The correct answer is: Increased retention of water

When antidiuretic hormone (ADH) is secreted, it primarily leads to increased retention of water in the body. ADH, also known as vasopressin, is produced in the hypothalamus and released from the posterior pituitary gland in response to high plasma osmolality or low blood volume. Its main action occurs in the kidneys, specifically in the collecting ducts, where it promotes the reabsorption of water back into the bloodstream. This reabsorption process helps to concentrate the urine, reducing the amount of water excreted, and leads to an increase in the volume of blood plasma. As a result, this action has the overall effect of conserving water, thus enhancing the body’s fluid balance and improving hydration status. Increased retention of water consequently helps to dilute the serum sodium concentration, potentially impacting electrolyte levels but not necessarily lowering them. This physiological response is crucial for maintaining homeostasis, especially in situations such as dehydration, where the body requires conservation of water to prevent further fluid loss and maintain adequate circulation.