As way of title explanation, the phytocannabinoids are the THC,CBD and others that come from the plant while the Endocannabinoids, Anandamide and 2-AG (THC and CBD analogs in that order) are made in our brains.
In my experience, when an external hormone or “transmitter” is given to a patient for replacement therapy, it is because the patient is not producing or releasing an adequate amount, or their receptors are no longer sensitive to the “hormone” or other ligand. When the external or, for example, oral thyroid medicine is taken, the patient’s thyroid is suppressed and stops making it’s own internal or “endogenous” version of the hormon, in this case, Levo Thyroxine.
The same is true for estrogen, testosterone, cortisol, etc etc.
When it comes to phyto-CBD, when it reaches the brain, in addition to it’s binding to many other receptors and blocking others, it induces the production and release of our own internal 2-AG. 2-AG is also unusual in that it is created “on the fly” and not stored for release. I am not able to intelligently speculate as to why this occurs with 2-AG and what the implications are, but will do so anyway. In GENERAL, when ligands, or communicators/neurotransmitters in the brain, are stored, they are stored prior to release, at least in part because they are in adequate supply. I would SPECULATE, and need information I have not been able to find yet, that not requiring storage, MIGHT be in part because it is in low supply?? IF, and again I say IF, this is the case, it would help explain a lot as to why so many patients respond in so many ways to tiny doses of whole plant CBD.