Several papers show that having to urinate frequently at night is often caused by low levels of antidiuretic hormone (1,2) and that taking that hormone can control this condition (3).
During the day, your kidneys clean your body by producing large amounts of urine. When you go to sleep at night, your brain produces large amounts of a hormone called anti-diuretic hormone or ADH for short, that shuts down your kidneys so you can sleep at night. As you age, your brain produces less ADH at night, so many older people have to urinate at night. Taking antidiuretic hormone nasal sprays or pills can help these people sleep through the night.
Even men who have frequent night-time urination after prostate surgery have reduced levels of ADH and can be cured by taking that hormone at bedtime (1). A potential serious side effect is seizures from taking too much water with ADH (4). So, if you take a 400 mg ADH pill or a single ADH nasal spray at bedtime, do not drink fluids after 6 PM.