AmberAmber,
The problem with that reasoning is, bloods don’t get drawn every day but only once in a while. To dose a patient based on that reasoning, means that a child or adult may be getting second - rate treatment over the longterm, when in fact the blood tests only get done rarely in comparison.
Have a look at a few cortisol and growth hormone circadian rhythm charts and you will see the problem with the large dose being at night.