Antidiuretic hormone (ADH)

"Anti" means against, and "diuresis" means passing a lot of urine. So ADH works against losing too much water. It is released from the back part of the pituitary gland. It acts on the tubules of the kidney, which then return more water to the blood.

• Body short of water: more ADH, so less urine, and it is darker.
• Body has plenty of water: less ADH, so more urine, and it is paler.
• Too little ADH over a long time: a condition called diabetes insipidus, with large amounts of watery urine.

A small example

On a hot day you sweat a lot and drink little. Your pituitary releases more ADH. Your kidneys save water, and you pass only a little dark urine. In winter, with little sweating, you pass more urine.

Where marks go

The 2025 ICSE Biology paper set an assertion and reason: too little ADH means more urination, because ADH makes the tubules reabsorb water. Both were true. In CISCE's report on the 2025 Biology paper, examiners say candidates could not link the hormone to the kidney tubules. In 2024, CISCE's report names confusion between adrenaline and vasopressin.

The 2027 specimen paper also tests where ADH comes from. In an odd-one-out set, ADH is the odd one because the others come from the front lobe of the pituitary. See specimen papers.

About the author

Deepti Sardana

Founder Member & Academic Lead

An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.

Deepti Sardana on LinkedIn