I could write a whole page on this but I will keep it simple. DK is right, it is dangerous after awhile to consume melatonin, especially any dosage than normal which is 5 to 25 MICROgrams. When you start taking melatonin, your body slowly stops making it's own because you are taking it artifically and the body doesn't need to produce anymore if it's already coming in.
Melatonin is a "Dark Hormone" which tells us it's time to sleep and for the nocturnal animals ,it's time to get up. When your cortisol levels are high and serotonin levels are low, you will not produce adequate amount of melatonin to help you sleep. When you have trouble falling asleep, you will have less chance of releasing GH. Your GH is released between 10pm-2am and then between 2am-6am, your psychological repair is in motion. Taking doses of Melatonin of 3mgs and higher, produce blood levels 10 to 30 times higher, which is very dangerous.
The continual release of stress hormones will prevent this from happening. Further, a brightly lit house, late night tv and working late into the evening will keep levels of stress hormones high past sundown. Fluorescent lights, TV and computer screens flicker on and off between 60 and 120 cycles per second, which interprets as morning sunlight. Since cortisol can take several hours to clear from your blood stream, this will also prevent melatonin and other growth/immune hormones, cutting into your immune system's valuable repair time.
If you go to bed after midnight you've already missed over two hours of your physical repair cycle, which, as I said before, should start around 10pm.
So the best way to get your natural GH to work, go to bed by 10pm.....