Wikipedia is a fucking joke. Melatonin is a hormone. Most of the hormones in the body are governed by negative feedback, which works like your household thermostat. Say you set your thermostat to 72 degrees and the room temperature is 69 degrees. The heater kicks in to warm the room up. When the temperature reaches 72 degrees, the heat shuts off until the temperature drops again. Administering hormones can actually shut off our body’s hormonal negative feedback loop. It’s like heating a room by a space heater and the furnace shuts off because it isn’t needed. I would stay away from melatonin as there are much better ways to get some sleep.