HGH, human growth hormone.. basically you can increase it naturally.
1 - Sleep more
2 - Don't eat 2-to-3 hours before sleeping
3 - Go on a temporary fast or Do intermittent fasting
4 - Do intense workouts
5 - Combine 4 & 5
6 - Lose weight
7 - Make your body produce L-Dopa
8 - Clean out your liver
9 - Laugh more
Read more here:
Top 9 ways to naturally increase your Human growth hormone (HGH)