Antidiuretic hormone (ADH) is a chemical produced in the brain that causes the kidneys to release less water, decreasing the amount of urine produced. A high ADH level causes the body to produce less urine. A low level results in greater urine production.
Normally, the amount of ADH in the body is higher during the night. This helps prevent urination while you are sleeping. But if the levels of ADH remain low during the night, the body will produce large amounts of urine, so urination during the night is more likely.
Sometimes this hormone system develops slowly in children and prevents the normal nighttime increase in ADH. This can increase the risk of bed-wetting during the night. Over time, this problem usually gets better on its own.