It doesn’t matter if you need to wake up at 5 a.m. everyday or 9 a.m., you just need to be consistent. According to WomentoWomen.com, the hypothalamus controls your inner circadian clock, which in turn regulates adrenal hormone levels including cortisol. Basically, your body has a system that monitors time, including seasonal changes and changes in light during the day and night. That system works with your adrenal glands to determine when it is time for you to sleep, and when it is time for you to be awake.
The ACTH hormone and cortisol naturally want to spike when your body thinks it should wake up. If you have a consistent wake up time, then these hormones will start to give you a natural rush of energy, therefore acting as your inner alarm clock.