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. High levels of ADH prevent urination throughout the night. Low levels of ADH mean that the body will produce large amounts of urine, so going to the bathroom during the night is likely.
A developmental immaturity, which usually resolves on its own over time, may prevent the normal nighttime increase of ADH.
WebMD Medical Reference from Healthwise