Around 11pm to 2am, growth hormones are released the most. but how our body know when is 11pm or 12am or 2am or 4am or 5pm to release growth hormones.

Master clock : Our normal circadian rhythm/cycles are controlled by a master clock system located in the pineal gland. That's controlled by light receptors from the retina. What can throw this off is constant use of computers late at night, giving off a blue wavelength, which decreases melatonin production, which is the signal needed to get the process of sleep going. Growth hormone levels increase when cortisol levels are lowest at that time of night between 11 pm-2 am, not when it is the highest.