The hypothalamus.
It is a relay station for serotonin extending into your frontal lobes.
It is also the director of the entire endocrine and adrenal system.
This is where the true magic, and damage, of MDMA occurs.
Quite literally - during recovery from neurotoxic doses, the hypothalamus is hyperinnervated by serotonin axons.
They collapse during the initial months from the cortex and never return again.
A minor, controlled version of this MAY be occurring with a few axons every time you roll.
While this cannot be detected, it is certain that they hypothalamus is reacting to the sudden increase in serotonin by directing the adrenals to release MASSIVE amounts of cortisol.
This increases metabolism of serotonin in the brain, and when this starts to finally drop, the hypothalamus directs the pituitary to stop ADH release and begin oxytocin and prolactin.
The hypothalamus also controls your heart-rate.
And digestion, body temperature...
Just a few months before I had serious serotonin syndrome that i am still recovering from - I had chest pain.
Since I was working out I associated it with pushups, but it only hurt on my left side.
One day it bothered me badly enough that I went to the ER and had it checked out.
Nothing.
The next time I had chest pain was during the onset of SS!
And it was SEVERE chest pain - what I would expect a heart-attack to feel like.
Serotonin was certainly hyper-innervating my hypothalamus that night!
There is your answer: neurotoxicity.
Stop using MDMA for a long time.
Like a year.
It WILL get worse, I promise you that.