The absence of anti-diuretic hormone in humans results in

1. Analyze the question The question asks what happens when anti-diuretic hormone (ADH) is absent. ADH is also called vasopressin.

2. Explain the concept

• ADH is made in the hypothalamus and released from the posterior pituitary gland.
• It acts on the distal convoluted tubule and collecting duct of the nephron, making them more permeable to water.
• This increases water reabsorption into the blood, so less water is lost and the urine becomes concentrated.

3. Step-by-step solution

• Without ADH, the tubules stay impermeable to water, so little water is reabsorbed.
• The kidney then produces a large volume of dilute urine. This condition is called diabetes insipidus.
• The body loses a lot of water, causing severe dehydration and intense thirst.

Now check the options:

• A. Decreasing dehydration: wrong, because water loss increases.
• B. Drastic dehydration: matches the large water loss.
• C. Eliminating dehydration: wrong, the opposite of what happens.
• D. Increasing dehydration: this is also in the right direction, but it is less precise. "Drastic" describes the severe, extreme water loss seen in ADH absence.

4. Answer B. Drastic dehydration

5. Exam tip Remember: "Anti-diuretic" means "against making lots of urine." If ADH is absent, the kidney makes lots of dilute urine and the body dries out. ADH present means water is saved, and ADH absent means water is lost. When two options both point the right way, as B and D do here, pick the one that best describes the severity of the condition.